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Ai2 1,337

87338038

10.2307/1447745

Freeze Tolerance and Postfreeze Recovery in the Frog Pseudacris crucifer

This study characterizes freeze tolerance and postfreeze recovery in the frog Pseudacris crucifer. We collected frogs from Pennsylvania during the autumns of 1994 and 1995. All experiments occurred in the laboratory and employed a freezing temperature of -1.5 C. This treatment froze 45% of the body water in these frogs, and they were clearly tolerant of internal freezing. However, their survival was inversely proportional to freeze duration (3 day = 85.0%, 7 day = 52.6%, and 28 day = 0%). Cutaneous blood flow, breathing, hind-leg retraction, righting reflex, and jumping ability returned to surviving frogs within 24-48 h following the conclusion of a 3-day freeze. Complex behavioral responses (e.g., jumping) required more time to return than did basic physiological functions (e.g., cutaneous blood flow). Interestingly, rates of oxygen consumption were not altered during the recovery period with respect to the prefreeze value. This study indicates that the freezing survival of P crucifer is markedly influenced by the duration of the freeze episode, which may be an important ecological limitation during winters having few intervening thaws. Recovering frogs require 1-2 days to fully regain complex motor responses; whereas vital functions are restored quickly, and oxygen consumption is not measurably altered during this period.

Copeia

17823270

10.1099/13500872-145-2-283

Evidence that halogenated furanones from Delisea pulchra inhibit acylated homoserine lactone (AHL)-mediated gene expression by displacing the AHL signal from its receptor protein.

Acylated homoserine lactone (AHL)-mediated gene expression controls phenotypes involved in colonization, often specifically of higher organisms, in both marine and terrestrial environments. The marine red alga Delisea pulchra produces halogenated furanones which resemble AHLs structurally and show inhibitory activity at ecologically realistic concentrations in AHL bioassays. Evidence is presented that halogenated furanones displace tritiated OHHL [N-3-(oxohexanoyl)-L-homoserine lactone] from Escherichia coli cells overproducing LuxR with potencies corresponding to their respective inhibitory activities in an AHL-regulated bioluminescence assay, indicating that this is the mechanism by which furanones inhibit AHL-dependent phenotypes. Alternative mechanisms for this phenomenon are also addressed. General metabolic disruption was assessed with two-dimensional PAGE, revealing limited non-AHL-related effects. A direct chemical interaction between the algal compounds and AHLs, as monitored by 1H NMR spectroscopy, was shown not to occur in vitro. These results support the contention that furanones, at the concentrations produced by the alga, can control bacterial colonization of surfaces by specifically interfering with AHL-mediated gene expression at the level of the LuxR protein.

Microbiology

9146317

10.1371/JOURNAL.PONE.0007995

Coral Skeletons Defend against Ultraviolet Radiation

Background Many coral reef organisms are photosynthetic or have evolved in tight symbiosis with photosynthetic symbionts. As such, the tissues of reef organisms are often exposed to intense solar radiation in clear tropical waters and have adapted to trap and harness photosynthetically active radiation (PAR). High levels of ultraviolet radiation (UVR) associated with sunlight, however, represent a potential problem in terms of tissue damage. Methodology/Principal Findings By measuring UVR and PAR reflectance from intact and ground bare coral skeletons we show that the property of calcium carbonate skeletons to absorb downwelling UVR to a significant extent, while reflecting PAR back to the overlying tissue, has biological advantages. We placed cnidarians on top of bare skeletons and a UVR reflective substrate and showed that under ambient UVR levels, UVR transmitted through the tissues of cnidarians placed on top of bare skeletons were four times lower compared to their counterparts placed on a UVR reflective white substrate. In accordance with the lower levels of UVR measured in cnidarians on top of coral skeletons, a similar drop in UVR damage to their DNA was detected. The skeletons emitted absorbed UVR as yellow fluorescence, which allows for safe dissipation of the otherwise harmful radiation. Conclusions/Significance Our study presents a novel defensive role for coral skeletons and reveals that the strong UVR absorbance by the skeleton can contribute to the ability of corals, and potentially other calcifiers, to thrive under UVR levels that are detrimental to most marine life.

PLOS ONE

11567277

10.1103/PHYSREVLETT.103.184501

Self-propelled dropwise condensate on superhydrophobic surfaces.

In conventional dropwise condensation on a hydrophobic surface, the condensate drops must be removed by external forces for continuous operation. This Letter reports continuous dropwise condensation spontaneously occurring on a superhydrophobic surface without any external forces. The spontaneous drop removal results from the surface energy released upon drop coalescence, which leads to a surprising out-of-plane jumping motion of the coalesced drops at a speed as high as 1 m/s. The jumping follows an inertial-capillary scaling and gives rise to a micrometric average diameter at steady state.

Physical Review Letters

40995892

10.1007/S00468-001-0153-3

Salt allocation during leaf development and leaf fall in mangroves

Abstract. By taking samples along individual branches and measuring leaf size, thickness and Na+ and K+ concentrations, we have shown in Bruguiera cylindrica, Avicennia rumphiana and Avicennia marina that there are two phases of salt accumulation by leaves. This is confirmed by re-analysis of published data for other species. The first phase is a rapid increase in leaf content as it grows from bud to maturity; the second is a slower but continuous change in quantity in the leaf, via changes in ion concentration and/or in leaf thickening. Leaf thickening must not be overlooked in estimating changes in leaf contents with age. Generally, leaf Na+ content increases significantly, and K+ content falls slightly. Mangrove leaves thus continue as sinks for Na+ throughout their lifetime. At the end of a leaf's life, just before abscission, no burst of salt accumulation has been found. Yellow, senescent leaves do not have higher Na+ than old green ones. We point out that leaf drop involves losing both salt and biomass, not just salt, and hence does not reduce the salt concentration in the plant. We conclude that leaf drop is not a salt excretion mechanism, but is simply the point in time at which the leaf ceases to accumulate salt. Using a simple model, the contribution to salt accumulation of slowly accumulated Na+ by mature leaves has been calculated. For B. cylindrica, the most extensively studied species, 60% of the salt in the leaf is accumulated slowly in the mature phase, thus more than during the initial phase of rapid expansion growth. The limited data suggest that gland-bearing species show smaller changes in mature leaf Na+ content than do gland-less species.

Trees-structure and Function

5448884

10.1126/SCIENCE.1165939

Serotonin Mediates Behavioral Gregarization Underlying Swarm Formation in Desert Locusts

Desert locusts, Schistocerca gregaria, show extreme phenotypic plasticity, transforming between a little-seen solitarious phase and the notorious swarming gregarious phase depending on population density. An essential tipping point in the process of swarm formation is the initial switch from strong mutual aversion in solitarious locusts to coherent group formation and greater activity in gregarious locusts. We show here that serotonin, an evolutionarily conserved mediator of neuronal plasticity, is responsible for this behavioral transformation, being both necessary if behavioral gregarization is to occur and sufficient to induce it. Our data demonstrate a neurochemical mechanism linking interactions between individuals to large-scale changes in population structure and the onset of mass migration.

Science

32152006

10.1088/1748-3182/6/4/046005

Grip and detachment of locusts on inverted sandpaper substrates.

Locusts (Locusta migratoria manilensis) are characterized by their strong flying and grasping ability. Research on the grasping mechanism and behaviour of locusts on sloping substrates plays an important role in elucidating the mechanics of hexapod locomotion. Data on the maximum angles of slope at which locusts can grasp stably (critical angles of detachment) were obtained from high-speed video recordings at 215 fps. The grasping forces were collected by using two sensors, in situations where all left legs were standing on one and the right legs on the other sensor plate. These data were used to illustrate the grasping ability of locusts on slopes with varying levels of roughness. The grasping morphologies of locusts' bodies and tarsi were observed, and the surface roughness as well as diameters of their claw tips was measured under a microscope to account for the grasping mechanism of these insects on the sloping substrate. The results showed that the claw tips and part of the pads were in contact with the inverted substrate when the mean particle diameter was in the range of 15.3-40.5 µm. The interaction between pads and substrates may improve the stability of contact, and claw tips may play a key role in keeping the attachment reliable. A model was developed to explain the significant effects of the relative size of claw tips and mean particle diameter on grasping ability as well as the observed increase in lateral force (2.09-4.05 times greater than the normal force during detachment) with increasing slope angle, which indicates that the lateral force may be extremely important in keeping the contact reliable. This research lays the groundwork for the probable design and development of biomimetic robotics.

Bioinspiration & Biomimetics

97479539

10.1039/C1EE01753E

On the electrical conductivity of microbial nanowires and biofilms

Dissimilatory metal-reducing bacteria (DMRB), such as Geobacter and Shewanella spp., occupy a distinct metabolic niche in which they acquire energy by coupling oxidation of organic fuels with reduction of insoluble extracellular electron acceptors (i.e., minerals). Their unique extracellular electron transfer (EET) capabilities extend to reduction of anodes (electrodes maintained at sufficiently positive potentials) on which they form persistent, electric current generating biofilms. One hypothesis describing the mechanism of EET by Geobacter and Shewanella spp. involves superexchange in which electrons are conducted by a succession of electron transfer reactions among redox proteins associated with the outer cell membranes, aligned along pilus-like filaments (e.g.pili), and/or throughout the extracellular matrix. Here we present theory, previously developed to describe superexchange within abiotic redox polymers, to describe superexchange within DMRB biofilms grown on anodes. We show that this theory appears to apply to recent ex situ measurements of electrical conductivity by individual pilus-like filaments of S. oneidensis MR-1 and G. sulfurreducensDL1, referred to as microbial nanowires. Microbial nanowires have received much recent attention because they are thought by some to impart electrical conductivity to DMRB biofilms and because of the prospect of microbe-produced conductive nanomaterials. We also show that this theory appears to apply to preliminary in situ demonstration of electrical conductivity of an anode-grown G. sulfurreducensDL1 biofilm. Based on these results we suggest a role for nanowires of S. oneidensis and G. sulfurreducens in biofilm conductivity.

Energy and Environmental Science

8089722

10.1073/PNAS.1016157108

Adaptive evolution of threonine deaminase in plant defense against insect herbivores

Gene duplication is a major source of plant chemical diversity that mediates plant–herbivore interactions. There is little direct evidence, however, that novel chemical traits arising from gene duplication reduce herbivory. Higher plants use threonine deaminase (TD) to catalyze the dehydration of threonine (Thr) to α-ketobutyrate and ammonia as the committed step in the biosynthesis of isoleucine (Ile). Cultivated tomato and related Solanum species contain a duplicated TD paralog (TD2) that is coexpressed with a suite of genes involved in herbivore resistance. Analysis of TD2-deficient tomato lines showed that TD2 has a defensive function related to Thr catabolism in the gut of lepidopteran herbivores. During herbivory, the regulatory domain of TD2 is removed by proteolysis to generate a truncated protein (pTD2) that efficiently degrades Thr without being inhibited by Ile. We show that this proteolytic activation step occurs in the gut of lepidopteran but not coleopteran herbivores, and is catalyzed by a chymotrypsin-like protease of insect origin. Analysis of purified recombinant enzymes showed that TD2 is remarkably more resistant to proteolysis and high temperature than the ancestral TD1 isoform. The crystal structure of pTD2 provided evidence that electrostatic interactions constitute a stabilizing feature associated with adaptation of TD2 to the extreme environment of the lepidopteran gut. These findings demonstrate a role for gene duplication in the evolution of a plant defense that targets and co-opts herbivore digestive physiology.

Proceedings of the National Academy of Sciences of the United States of America

11592364

10.1007/S004250100576

Biochemical analysis of elastic and rigid cuticles of Cirsium horridulum

Abstract. The cuticle is a complex structure of soluble lipids, lipid polymers and polysaccharides. In addition to its functions to reduce water loss and provide a protective barrier, its mechanical properties may be significant to plant growth and development. We investigated the cuticle of Cirsium horridulum Michx. because of its involvement in the thigmonastic contraction of staminal filaments. The staminal filaments and portions of the style are surrounded by a highly elastic cuticle in contrast to the rigid cuticle of the corolla and leaves. Our aim was to determine if the biochemical composition affected the elasticity of the cuticle. We discovered that the ratio of carbohydrates to lipids is 1:7 in floral parts but 2:1 in leaf cuticle. Esterified cutin components represented about 80% of the cuticle and di-hydroxyhexadecanoic acids were the major monomers of cutin, regardless of origin. The cutin of elastic tissues is characterized by a higher content of tri-hydroxy monomers than the cutin of rigid tissues. The data suggest that hydroxyl groups enhance the hydrophilic character of the cuticle and contribute to cuticular elasticity.

Planta

206512036

10.1126/SCIENCE.1156023

Surface Tension Transport of Prey by Feeding Shorebirds: The Capillary Ratchet

The variability of bird beak morphology reflects diverse foraging strategies. One such feeding mechanism in shorebirds involves surface tension–induced transport of prey in millimetric droplets: By repeatedly opening and closing its beak in a tweezering motion, the bird moves the drop from the tip of its beak to its mouth in a stepwise ratcheting fashion. We have analyzed the subtle physical mechanism responsible for drop transport and demonstrated experimentally that the beak geometry and the dynamics of tweezering may be tuned to optimize transport efficiency. We also highlight the critical dependence of the capillary ratchet on the beak's wetting properties, thus making clear the vulnerability of capillary feeders to surface pollutants.

Science

16303094

10.1016/J.CUB.2012.12.010

Adaptive aerial righting during the escape dropping of wingless pea aphids

Summary Pea aphids ( Acyrthosiphon pisum ) are small sap-sucking insects that live on plants in colonies containing mostly wingless individuals. They often escape predators, parasitoids and grazing mammalian herbivores by dropping off the plant [1,2], avoiding immediate danger but exposing themselves to ground predators, starvation and desiccation [3]. We show here that dropping pea aphids land on their legs, regardless of their initial orientation on the plant (like a defenestrated cat), by rotating their body during the fall. This righting ability is intriguing, as wingless aphids have no specialized structures for maneuvering in mid-air. Instead, they assume a stereotypic posture which is aerodynamically stable only when the aphids fall right-side up. Consequently, the body passively rotates to the stable upright orientation, improving the chance of clinging to leaves encountered on the way down and lowering the danger of reaching the ground.

Current Biology

8479271

10.1111/J.0022-202X.2004.23213.X

Stratum corneum keratin structure, function, and formation: the cubic rod-packing and membrane templating model.

A new model for stratum corneum keratin structure, function, and formation is presented. The structural and functional part of the model, which hereafter is referred to as "the cubic rod-packing model", postulates that stratum corneum keratin intermediate filaments are arranged according to a cubic-like rod-packing symmetry with or without the presence of an intracellular lipid membrane with cubic-like symmetry enveloping each individual filament. The new model could account for (i) the cryo-electron density pattern of the native corneocyte keratin matrix, (ii) the X-ray diffraction patterns, (iii) the swelling behavior, and (iv) the mechanical properties of mammalian stratum corneum. The morphogenetic part of the model, which hereafter is referred to as "the membrane templating model", postulates the presence in cellular space of a highly dynamic small lattice parameter (<30 nm) membrane structure with cubic-like symmetry, to which keratin is associated. It further proposes that membrane templating, rather than spontaneous self-assembly, is responsible for keratin intermediate filament formation and dynamics. The new model could account for (i) the cryo-electron density patterns of the native keratinocyte cytoplasmic space, (ii) the characteristic features of the keratin network formation process, (iii) the dynamic properties of keratin intermediate filaments, (iv) the close lipid association of keratin, (v) the insolubility in non-denaturating buffers and pronounced polymorphism of keratin assembled in vitro, and (vi) the measured reduction in cell volume and hydration level between the stratum granulosum and stratum corneum. Further, using cryo-transmission electron microscopy on native, fully hydrated, vitreous epidermis we show that the subfilametous keratin electron density pattern consists, both in corneocytes and in viable keratinocytes, of one axial subfilament surrounded by an undetermined number of peripheral subfilaments forming filaments with a diameter of approximately 8 nm.

Journal of Investigative Dermatology

16640660

10.1371/JOURNAL.PONE.0140407

Mushrooms as Rainmakers: How Spores Act as Nuclei for Raindrops

Millions of tons of fungal spores are dispersed in the atmosphere every year. These living cells, along with plant spores and pollen grains, may act as nuclei for condensation of water in clouds. Basidiospores released by mushrooms form a significant proportion of these aerosols, particularly above tropical forests. Mushroom spores are discharged from gills by the rapid displacement of a droplet of fluid on the cell surface. This droplet is formed by the condensation of water on the spore surface stimulated by the secretion of mannitol and other hygroscopic sugars. This fluid is carried with the spore during discharge, but evaporates once the spore is airborne. Using environmental electron microscopy, we have demonstrated that droplets reform on spores in humid air. The kinetics of this process suggest that basidiospores are especially effective as nuclei for the formation of large water drops in clouds. Through this mechanism, mushroom spores may promote rainfall in ecosystems that support large populations of ectomycorrhizal and saprotrophic basidiomycetes. Our research heightens interest in the global significance of the fungi and raises additional concerns about the sustainability of forests that depend on heavy precipitation.

PLOS ONE

1707898

10.1086/653666

Geographical Variation in Bill Size across Bird Species Provides Evidence for Allen’s Rule

Allen’s rule proposes that the appendages of endotherms are smaller, relative to body size, in colder climates, in order to reduce heat loss. Empirical support for Allen’s rule is mainly derived from occasional reports of geographical clines in extremity size of individual species. Interspecific evidence is restricted to two studies of leg proportions in seabirds and shorebirds. We used phylogenetic comparative analyses of 214 bird species to examine whether bird bills, significant sites of heat exchange, conform to Allen’s rule. The species comprised eight diverse taxonomic groups—toucans, African barbets, Australian parrots, estrildid finches, Canadian galliforms, penguins, gulls, and terns. Across all species, there were strongly significant relationships between bill length and both latitude and environmental temperature, with species in colder climates having significantly shorter bills. Patterns supporting Allen’s rule in relation to latitudinal or altitudinal distribution held within all groups except the finches. Evidence for a direct association with temperature was found within four groups (parrots, galliforms, penguins, and gulls). Support for Allen’s rule in leg elements was weaker, suggesting that bird bills may be more susceptible to thermoregulatory constraints generally. Our results provide the strongest comparative support yet published for Allen’s rule and demonstrate that thermoregulation has been an important factor in shaping the evolution of bird bills.

The American Naturalist

86306824

10.1007/BF00438357

Morphological variations of Macrocystis pyrifera in the Falkland Islands in relation to environment and season

Some morphological characteristics of the giant kelp Macrocystis pyrifera in the Falkland Islands were studied from December 1985 until March 1987 in a shallow and relatively sheltered coastal zone and from December 1985 until January 1987 in a deeper offshore field exposed to swells. Seasonal fluctuations in lamina wet weight, density and form as well as pneumatocyst wet weight form and stipe density (i.e., wet weight per unit length) paralleled fluctuations in frond wet weight. Morphological differences between canopies of the giant kelp in the coastal zone and the offshore bed were probably mainly due to differences in water movement and depth between the two sites. Laminae and pneumatocysts of submersed-frond sites had different shapes than those of canopy-forming portions of fronds at the same sites, and their internodes were longer.

Marine Biology

18399685

10.1007/S11721-012-0067-2

Distributed graph coloring: an approach based on the calling behavior of Japanese tree frogs

Graph coloring—also known as vertex coloring—considers the problem of assigning colors to the nodes of a graph such that adjacent nodes do not share the same color. The optimization version of the problem concerns the minimization of the number of colors used. In this paper we deal with the problem of finding valid graphs colorings in a distributed way, that is, by means of an algorithm that only uses local information for deciding the color of the nodes. The algorithm proposed in this paper is inspired by the calling behavior of Japanese tree frogs. Male frogs use their calls to attract females. Interestingly, groups of males that are located near each other desynchronize their calls. This is because female frogs are only able to correctly localize male frogs when their calls are not too close in time. The proposed algorithm makes use of this desynchronization behavior for the assignment of different colors to neighboring nodes. We experimentally show that our algorithm is very competitive with the current state of the art, using different sets of problem instances and comparing to one of the most competitive algorithms from the literature.

Swarm Intelligence

12828690

10.1371/JOURNAL.PONE.0008806

The Advantages of a Tapered Whisker

The role of facial vibrissae (whiskers) in the behavior of terrestrial mammals is principally as a supplement or substitute for short-distance vision. Each whisker in the array functions as a mechanical transducer, conveying forces applied along the shaft to mechanoreceptors in the follicle at the whisker base. Subsequent processing of mechanoreceptor output in the trigeminal nucleus and somatosensory cortex allows high accuracy discriminations of object distance, direction, and surface texture. The whiskers of terrestrial mammals are tapered and approximately circular in cross section. We characterize the taper of whiskers in nine mammal species, measure the mechanical deflection of isolated felid whiskers, and discuss the mechanics of a single whisker under static and oscillatory deflections. We argue that a tapered whisker provides some advantages for tactile perception (as compared to a hypothetical untapered whisker), and that this may explain why the taper has been preserved during the evolution of terrestrial mammals.

PLOS ONE

4370356

10.1038/35070564

Hyperacute directional hearing in a microscale auditory system

The physics of sound propagation imposes fundamental constraints on sound localization: for a given frequency, the smaller the receiver, the smaller the available cues. Thus, the creation of nanoscale acoustic microphones with directional sensitivity is very difficult. The fly Ormia ochracea possesses an unusual ‘ear’ that largely overcomes these physical constraints; attempts to exploit principles derived from O. ochracea for improved hearing aids are now in progress. Here we report that O. ochracea can behaviourally localize a salient sound source with a precision equal to that of humans. Despite its small size and minuscule interaural cues, the fly localizes sound sources to within 2° azimuth. As the fly's eardrums are less than 0.5 mm apart, localization cues are around 50 ns. Directional information is represented in the auditory system by the relative timing of receptor responses in the two ears. Low-jitter, phasic receptor responses are pooled to achieve hyperacute timecoding. These results demonstrate that nanoscale/microscale directional microphones patterned after O. ochracea have the potential for highly accurate directional sensitivity, independent of their size. Notably, in the fly itself this performance is dependent on a newly discovered set of specific coding strategies employed by the nervous system.

Nature

86825313

10.1163/156853804322992814

Integumental water movement and rate of water ingestion during rain harvesting in the Texas horned lizard, Phrynosoma cornutum

Capture of rainfall on skin surfaces and its transport via capillary channels between scales to the mouth for drinking has been documented in a few agamid ( Moloch and Phrynocephalus ) and iguanid ( Phrynosoma spp.) lizards. Associated behaviors include a postural stance and jaw motions. This experimental study documents that rate of jaw opening and closing cycles is positively correlated with rate of water delivery to lizards' backs and to gain in mass of lizards attributable to drinking. The mean mass of water that can be held by the interscalar, capillary-flow system is correlated with body size, smaller lizards holding a larger percentage of their body mass in the rain-harvesting system. Ingestion mechanisms for water flow from the integumental channels to the mouth surfaces for drinking are discussed, with note being made of the possible roles of a fold of skin at the jaw angle (at the postlabial scales) and tongue actions. Recent hatchlings exhibit rain-harvesting behavior, suggesting its innate nature.

Amphibia-reptilia

87191964

10.2307/2388018

Behavioral and morphological adaptations of a tropical plant to high rainfall

Machaerium arboireum (Leguminosae), a liana of Panamanian lowland forests, sheds water from upper leaflet surfaces through thigmonastic and nyctinastic leaf movements. Experiments show that leaflets with acuminate tips have an improved water-shedding ability. A STUDY WAS CONDUCTED to test the effects of leaf shape and leaf movement on shedding of rain water by juvenile plants of Machaerium aorboreum (Jacq.) Vogel (Leguminosae), a liana of Panamanian lowland forests. The leaflets have acuminate tips ("driptips"), and exhibit both thigmonasty (movement in response to tacile stimuli) and nyctinasty (diurnal movement patterns). Thigmonasty also occurs in Mimosa pudica L. (Leguminosae), the "sensitive plant" (Roblin 1976), and many other tropical legumes The leaflets of Mimosa fold within a few seconds following gentle stimuli. Raindrops initiate thigmonastic responses in other tropical plants (von Denffer et al. 1976). The functional significance of this response has not been determined. Nyctinastic leaves may protect meristematic tissue from frost damage in some high-elevation plants (Smith 1974), but their adaptive significance in low-elevation tropical plants is undear (Darwin 1881, Satter and Galston 1971, Schwintzer 1971). Jungner (1891) was one of the first to regard drip-tips as an adaptation for rapid draining of the leaf surface. He observed that leaves with drip-tips dried more quickly, and were less overgrown with epiphyllae, than leaves without drip-tips. He believed that by facilitating water runoff, drip-tips kept the leaf surface relatively clear of spores of epiphyllae, and soluble substances which might encourage epiphyllae growth. Stahl (1898) showed that by removing the drip-tips he could increase the time required for a leaf to dry, but he doubted there was any correlation between drip-tips and the presence or absence of epiphyllae. He instead proposed that driptips functioned to prevent a lingering surface film of water, which would lower the surface temperature of the leaf, which in turn would slow the rate of transpiration by the plant. A low rate of transpiralPresent address: Department of Zoology, University of Iowa, Iowa City, Iowa 52242, U.S.A. tion, he reasoned, would slow the uptake of mineral salts by the roots, which would be disadvantageous to the plant. Shreve (1914), working in the understory in the montane forest of Jamaica, was unable to detect any difference in the rate of drying in leaves with driptips removed versus those with drip-tips intact. Richards (1966) maintains that Shreve worked with plants with atypical, abbreviated drip-tips, and that his results do not therefore disprove the hypothesis that drip-tips have a drying function. According to Richards and to Edmisten (1970), the controversy about the ecological significance of drip-tips remains unsolved.

Biotropica

6846483

10.1242/JEB.022343

Water homeostasis in bees, with the emphasis on sociality

SUMMARY Avenues of water gain and loss in bees are examined here at two levels of organisation: the individual and the colony. Compared with the majority of terrestrial insects, bees have a high water turnover. This is due to their nectar diet and, in larger species, substantial metabolic water production during flight, counteracted by high evaporative and excretory losses. Water fluxes at the colony level can also be very high. When incoming nectar is dilute, honeybees need to remove large volumes of water by evaporation. On the other hand, water is not stored in the nest and must be collected for evaporative cooling and for feeding the brood. Water regulation has many similarities at individual and colony levels. In particular, manipulation of nectar or water on the tongue is extensively used by bees to increase evaporation for either food-concentrating or cooling purposes.

The Journal of Experimental Biology

8238868

10.1103/PHYSREVE.73.041916

Optical properties of the iridescent organ of the comb-jellyfish Beroë cucumis (Ctenophora).

Using transmission electron microscopy, analytical modeling, and detailed numerical simulations, the iridescence observed from the comb rows of the ctenophore Beroë cucumis was investigated. It is shown that the changing coloration which accompanies the beating of comb rows as the animal swims can be explained by the weakly-contrasted structure of the refractive index induced by the very coherent packing of locomotory cilia. The colors arising from the narrow band-gap reflection are shown to be highly saturated and, as a function of the incidence angle, cover a wide range of the visible and ultraviolet spectrum. The high transparency of the structure at the maximal bioluminescence wavelength is also explained.

Physical Review E

17861923

10.1371/JOURNAL.PONE.0011234

Bioprospecting Finds the Toughest Biological Material: Extraordinary Silk from a Giant Riverine Orb Spider

Background Combining high strength and elasticity, spider silks are exceptionally tough, i.e., able to absorb massive kinetic energy before breaking. Spider silk is therefore a model polymer for development of high performance biomimetic fibers. There are over 41.000 described species of spiders, most spinning multiple types of silk. Thus we have available some 200.000+ unique silks that may cover an amazing breadth of material properties. To date, however, silks from only a few tens of species have been characterized, most chosen haphazardly as model organisms (Nephila) or simply from researchers' backyards. Are we limited to ‘blindly fishing’ in efforts to discover extraordinary silks? Or, could scientists use ecology to predict which species are likely to spin silks exhibiting exceptional performance properties? Methodology We examined the biomechanical properties of silk produced by the remarkable Malagasy ‘Darwin's bark spider’ (Caerostris darwini), which we predicted would produce exceptional silk based upon its amazing web. The spider constructs its giant orb web (up to 2.8 m2) suspended above streams, rivers, and lakes. It attaches the web to substrates on each riverbank by anchor threads as long as 25 meters. Dragline silk from both Caerostris webs and forcibly pulled silk, exhibits an extraordinary combination of high tensile strength and elasticity previously unknown for spider silk. The toughness of forcibly silked fibers averages 350 MJ/m3, with some samples reaching 520 MJ/m3. Thus, C. darwini silk is more than twice tougher than any previously described silk, and over 10 times better than Kevlar®. Caerostris capture spiral silk is similarly exceptionally tough. Conclusions Caerostris darwini produces the toughest known biomaterial. We hypothesize that this extraordinary toughness coevolved with the unusual ecology and web architecture of these spiders, decreasing the likelihood of bridgelines breaking and collapsing the web into the river. This hypothesis predicts that rapid change in material properties of silk co-occurred with ecological shifts within the genus, and can thus be tested by combining material science, behavioral observations, and phylogenetics. Our findings highlight the potential benefits of natural history–informed bioprospecting to discover silks, as well as other materials, with novel and exceptional properties to serve as models in biomimicry.

PLOS ONE

5801832

10.1098/RSIF.2008.0395.FOCUS

Iridescence: a functional perspective

In animals, iridescence is generated by the interaction of light with biological tissues that are nanostructured to produce thin films or diffraction gratings. Uniquely among animal visual signals, the study of iridescent coloration contributes to biological and physical sciences by enhancing our understanding of the evolution of communication strategies, and by providing insights into physical optics and inspiring biomimetic technologies useful to humans. Iridescent colours are found in a broad diversity of animal taxa ranging from diminutive marine copepods to terrestrial insects and birds. Iridescent coloration has received a surge of research interest of late, and studies have focused on both characterizing the nanostructures responsible for producing iridescence and identifying the behavioural functions of iridescent colours. In this paper, we begin with a brief description of colour production mechanisms in animals and provide a general overview of the taxonomic distribution of iridescent colours. We then highlight unique properties of iridescent signals and review the proposed functions of iridescent coloration, focusing, in particular, on the ways in which iridescent colours allow animals to communicate with conspecifics and avoid predators. We conclude with a brief overview of non-communicative functions of iridescence in animals. Despite the vast amount of recent work on animal iridescence, our review reveals that many proposed functions of iridescent coloration remain virtually unexplored, and this area is clearly ripe for future research.

Journal of the Royal Society Interface

10028869

10.1371/JOURNAL.PONE.0003237

The Fastest Flights in Nature: High-Speed Spore Discharge Mechanisms among Fungi

Background A variety of spore discharge processes have evolved among the fungi. Those with the longest ranges are powered by hydrostatic pressure and include “squirt guns” that are most common in the Ascomycota and Zygomycota. In these fungi, fluid-filled stalks that support single spores or spore-filled sporangia, or cells called asci that contain multiple spores, are pressurized by osmosis. Because spores are discharged at such high speeds, most of the information on launch processes from previous studies has been inferred from mathematical models and is subject to a number of errors. Methodology/Principal Findings In this study, we have used ultra-high-speed video cameras running at maximum frame rates of 250,000 fps to analyze the entire launch process in four species of fungi that grow on the dung of herbivores. For the first time we have direct measurements of launch speeds and empirical estimates of acceleration in these fungi. Launch speeds ranged from 2 to 25 m s−1 and corresponding accelerations of 20,000 to 180,000 g propelled spores over distances of up to 2.5 meters. In addition, quantitative spectroscopic methods were used to identify the organic and inorganic osmolytes responsible for generating the turgor pressures that drive spore discharge. Conclusions/Significance The new video data allowed us to test different models for the effect of viscous drag and identify errors in the previous approaches to modeling spore motion. The spectroscopic data show that high speed spore discharge mechanisms in fungi are powered by the same levels of turgor pressure that are characteristic of fungal hyphae and do not require any special mechanisms of osmolyte accumulation.

PLOS ONE

322472

10.3389/FPLS.2012.00001

Protein Phylogenetic Analysis of Ca2+/cation Antiporters and Insights into their Evolution in Plants

Cation transport is a critical process in all organisms and is essential for mineral nutrition, ion stress tolerance, and signal transduction. Transporters that are members of the Ca2+/cation antiporter (CaCA) superfamily are involved in the transport of Ca2+ and/or other cations using the counter exchange of another ion such as H+ or Na+. The CaCA superfamily has been previously divided into five transporter families: the YRBG, Na+/Ca2+ exchanger (NCX), Na+/Ca2+, K+ exchanger (NCKX), H+/cation exchanger (CAX), and cation/Ca2+ exchanger (CCX) families, which include the well-characterized NCX and CAX transporters. To examine the evolution of CaCA transporters within higher plants and the green plant lineage, CaCA genes were identified from the genomes of sequenced flowering plants, a bryophyte, lycophyte, and freshwater and marine algae, and compared with those from non-plant species. We found evidence of the expansion and increased diversity of flowering plant genes within the CAX and CCX families. Genes related to the NCX family are present in land plant though they encode distinct MHX homologs which probably have an altered transport function. In contrast, the NCX and NCKX genes which are absent in land plants have been retained in many species of algae, especially the marine algae, indicating that these organisms may share “animal-like” characteristics of Ca2+ homeostasis and signaling. A group of genes encoding novel CAX-like proteins containing an EF-hand domain were identified from plants and selected algae but appeared to be lacking in any other species. Lack of functional data for most of the CaCA proteins make it impossible to reliably predict substrate specificity and function for many of the groups or individual proteins. The abundance and diversity of CaCA genes throughout all branches of life indicates the importance of this class of cation transporter, and that many transporters with novel functions are waiting to be discovered.

Frontiers in Plant Science

2638295

10.1073/PNAS.1108558108

Squalamine as a broad-spectrum systemic antiviral agent with therapeutic potential

Antiviral compounds that increase the resistance of host tissues represent an attractive class of therapeutic. Here, we show that squalamine, a compound previously isolated from the tissues of the dogfish shark (Squalus acanthias) and the sea lamprey (Petromyzon marinus), exhibits broad-spectrum antiviral activity against human pathogens, which were studied in vitro as well as in vivo. Both RNA- and DNA-enveloped viruses are shown to be susceptible. The proposed mechanism involves the capacity of squalamine, a cationic amphipathic sterol, to neutralize the negative electrostatic surface charge of intracellular membranes in a way that renders the cell less effective in supporting viral replication. Because squalamine can be readily synthesized and has a known safety profile in man, we believe its potential as a broad-spectrum human antiviral agent should be explored.

Proceedings of the National Academy of Sciences of the United States of America

9873597

10.1242/JEB.056093

The diving bell and the spider: the physical gill of Argyroneta aquatica

SUMMARY Argyroneta aquatica is a unique air-breathing spider that lives virtually its entire life under freshwater. It creates a dome-shaped web between aquatic plants and fills the diving bell with air carried from the surface. The bell can take up dissolved O2 from the water, acting as a ‘physical gill’. By measuring bell volume and O2 partial pressure (PO2) with tiny O2-sensitive optodes, this study showed that the spiders produce physical gills capable of satisfying at least their resting requirements for O2 under the most extreme conditions of warm stagnant water. Larger spiders produced larger bells of higher O2 conductance (GO2). GO2 depended on surface area only; effective boundary layer thickness was constant. Bells, with and without spiders, were used as respirometers by measuring GO2 and the rate of change in PO2. Metabolic rates were also measured with flow-through respirometry. The water–air PO2 difference was generally less than 10 kPa, and spiders voluntarily tolerated low internal PO2 approximately 1–4 kPa before renewal with air from the surface. The low PO2 in the bell enhanced N2 loss from the bell, but spiders could remain inside for more than a day without renewal. Spiders appeared to enlarge the bells in response to higher O2 demands and lower aquatic PO2.

The Journal of Experimental Biology

137022537

10.1016/S1369-7021(02)01237-3

Survival of the cheapest

Abstract Most of our resources, especially materials, are treated by economics as if the supply were infinite, when demonstrably it is not for those that are non-renewable. In his engineering, use of materials and energy, man lets design takes second place, whereas nature treats materials as expensive and designs with apparent care and attention to detail. This results in durable materials and cheap structures that are easy to recycle under ambient conditions. Examples illustrating this principle, which are given here, are drawn from both animals and plants with comments on the underlying mechanisms such as self-assembly of liquid crystal systems, use of composite structures, and control of fracture properties. The natural world, of which we are a significant part, has many examples of survival with minimum use of energy. These examples range from the production and use of materials to the organization of entire populations. But not all organisms exist in a half-lit, miserly half-life. Their (that is to say, our) driving purpose in life is to reproduce, and no organism (that is, me or you) would be here unless our parents had a strong urge to reproduce, something which we, mostly, inherit. So any way that we can have the largest number of surviving offspring will be favored. In doing this we are in competition with nearly all the other organisms in the vicinity. The ones with which we are overtly friendly are our immediate genetic (or to a lesser extent, social) relatives, and much has been made of the concept that it is our genes, rather than ourselves, that crave dominance.

Materials Today

85082644

10.1016/J.JEMBE.2008.06.036

Light inside sponges

Sponges are the most basal metazoan organisms. As sessile filter feeders in marine or freshwater habitats, they often live in close association with phototrophic microorganisms. Active photosynthesis by the associated microorganisms has been believed to be restricted to the outer tissue portion of the sponge hosts. However, phototrophic microorganisms have also been detected in deeper tissue regions. In many cases they are found around spicules, siliceous skelettal elements of demosponges and hexactinellids. The finding of phototrophic organisms seemingly assembled around spicules led to the hypothesis of a siliceous light transmission system in sponges. The principle ability to conduct light was already shown for sponge derived, explanted spicules. However it was not shown until now, that in deed sponges have a light transmission system, and can harbour photosynthetically active microorganisms in deeper tissue regions. Here we show for the first time, that, as hypothesized 13 year ago, sponge spicules in living specimens transmit light into deeper tissue regions. Our results demonstrate that in opposite to the actual opinion, photosynthetically active microorganisms can also live in deeper tissue regions, and not only directly beneath the surface, when a light transmission system (spicules) is present. Our results show the possibility of massive or globular sponges being supplied with photosynthetic products or pathways throughout their whole body, implying not only a more important role of these endobioses. Our findings also elucidate the in-situ function of a recently more and more interesting biomaterial, which is unique not only for its mechanical, electrical and optical properties. Biosilica is of special interest for the possibility to produce it enzymatically under environmental conditions.

Journal of Experimental Marine Biology and Ecology

23011211

10.1126/SCIENCE.AAA5099

Shared decision-making drives collective movement in wild baboons

Baboons follow the pack, not the leader How do groups of animals, including humans, make decisions that affect the entire group? Evidence collected from schooling animals suggests that the process is somewhat democratic, with nearest neighbors and the majority shaping overall collective behavior. In animals with hierarchical social structures such as primates or wolves, however, such democracy may be complicated by dominance. Strandburg-Peshkin et al. monitored all the individuals within a baboon troop continuously over the course of their daily activities. Even within this highly socially structured species, movement decisions emerged via a shared process. Thus, democracy may be an inherent trait of collective behavior. Science, this issue p. 1358 Democracy guides group decisions in baboons, even in the presence of strong social hierarchies. Conflicts of interest about where to go and what to do are a primary challenge of group living. However, it remains unclear how consensus is achieved in stable groups with stratified social relationships. Tracking wild baboons with a high-resolution global positioning system and analyzing their movements relative to one another reveals that a process of shared decision-making governs baboon movement. Rather than preferentially following dominant individuals, baboons are more likely to follow when multiple initiators agree. When conflicts arise over the direction of movement, baboons choose one direction over the other when the angle between them is large, but they compromise if it is not. These results are consistent with models of collective motion, suggesting that democratic collective action emerging from simple rules is widespread, even in complex, socially stratified societies.

Science

13428765

10.1111/J.1469-8137.2009.03069.X

Architecture of the wood-wide web: Rhizopogon spp. genets link multiple Douglas-fir cohorts.

*The role of mycorrhizal networks in forest dynamics is poorly understood because of the elusiveness of their spatial structure. We mapped the belowground distribution of the fungi Rhizopogon vesiculosus and Rhizopogon vinicolor and interior Douglas-fir trees (Pseudotsuga menziesii var. glauca) to determine the architecture of a mycorrhizal network in a multi-aged old-growth forest. *Rhizopogon spp. mycorrhizas were collected within a 30 x 30 m plot. Trees and fungal genets were identified using multi-locus microsatellite DNA analysis. Tree genotypes from mycorrhizas were matched to reference trees aboveground. Two trees were considered linked if they shared the same fungal genet(s). *The two Rhizopogon species each formed 13-14 genets, each colonizing up to 19 trees in the plot. Rhizopogon vesiculosus genets were larger, occurred at greater depths, and linked more trees than genets of R. vinicolor. Multiple tree cohorts were linked, with young saplings established within the mycorrhizal network of Douglas-fir veterans. A strong positive relationship was found between tree size and connectivity, resulting in a scale-free network architecture with small-world properties. *This mycorrhizal network architecture suggests an efficient and robust network, where large trees play a foundational role in facilitating conspecific regeneration and stabilizing the ecosystem.

New Phytologist

198156892

10.1646/0006-3606(2001)033[0188:ATOTFO]2.0.CO;2

A Test of the Function of Drip Tips1

Biotropica

83837478

10.1111/J.1529-8817.2010.00829.X

COMPOSITION OF EXTRACELLULAR POLYMERIC SUBSTANCES FROM PERIPHYTON ASSEMBLAGES IN THE FLORIDA EVERGLADES 1

In wetland habitats, periphyton is a common component of open‐water areas with species assemblage determined by local water quality. Extracellular polymeric substances (EPS) secreted by algae and bacteria give structure to periphyton, and differences in EPS chemistry affect the functional roles of these polymers. The Florida Everglades provide a unique opportunity to study compositional differences of EPS from distinctive algal assemblages that characterize areas of differing water chemistry. Water conservation area (WCA)‐1 is a soft‐water impoundment; periphyton was loosely associated with Utricularia stems and amorphous in structure, with a diverse desmid and diatom assemblage, and varying cyanobacterial abundance. Extracellular polymers were abundant and were loosely cell‐associated sheaths and slime layers in addition to tightly cell‐associated capsules. The EPS were complex heteropolysaccharides with significant saccharide residues of glucose, xylose, arabinose, and fucose. Carboxylic acids were also prominent, while ester sulfates and proteins were small components. Structured, cohesive cyanobacteria‐dominated periphyton was observed in WCA‐2A, a minerotrophic impoundment, and filaments were heavily encrusted with calcium carbonate and detrital matter. EPS were primarily cell‐associated sheaths, and polymer residues were dominated by glucose, xylose, fucose, and galactose, with uronic acids also a significant component of the polymers. Principal components analysis revealed that periphyton community assemblage determined the monosaccharide composition of EPS, which ultimately determines a range of biogeochemical processes within the periphyton.

Journal of Phycology

37853085

10.1016/J.PBI.2007.04.004

Suberin--a biopolyester forming apoplastic plant interfaces.

Suberized cell walls form physiologically important plant-environment interfaces because they act as barriers that limit water and nutrient transport and protect plants from invasion by pathogens. Plants respond to environmental stimuli by modifying the degree of suberization in root cell walls. Salt stress or drought-induced suberization leads to a decrease in radial water transport in roots. Although reinforced, suberized cell walls never act as absolutely impermeable barriers. Deeper insights into the structure and biosynthesis of suberin are required to elucidate what determines the barrier properties. Progress has been obtained from analytical methods that enabled the structural characterization of oligomeric building blocks in suberin, and from the opening of suberin research to molecular genetic approaches by the elucidation of the chemical composition and tissue distribution of suberin in the model species Arabidopsis.

Current Opinion in Plant Biology

10913886

10.1111/J.1365-3040.2009.02066.X

Mimosa pudica: Electrical and mechanical stimulation of plant movements.

Thigmonastic movements in the sensitive plant Mimosa pudica L., associated with fast responses to environmental stimuli, appear to be regulated through electrical and chemical signal transductions. The thigmonastic responses of M. pudica can be considered in three stages: stimulus perception, electrical signal transmission and induction of mechanical, hydrodynamical and biochemical responses. We investigated the mechanical movements of the pinnae and petioles in M. pudica induced by the electrical stimulation of a pulvinus, petiole, secondary pulvinus or pinna by a low electrical voltage and charge. The threshold value was 1.3-1.5 V of applied voltage and 2 to 10 microC of charge for the closing of the pinnules. Both voltage and electrical charge are responsible for the electro-stimulated closing of a leaf. The mechanism behind closing the leaf in M. pudica is discussed. The hydroelastic curvature mechanism closely describes the kinetics of M. pudica leaf movements.

Plant Cell and Environment

31421847

10.1002/JMOR.1051180206

Studies on the morphology and function of the skull in the boidae (Serpentes). Part II. Morphology and function of the jaw apparatus in Python sebae and Python molurus

Heads of the boid snakes Python sebae and Python molurus were dissected and the arthrology, myology and dentition studied. Living specimens of these species were observed and their feeding behavior analyzed by means of high‐ and regular‐speed motion pictures. Camera speeds of up to 400 frames per second permitted examination of the jaw movements during the striking and seizing of prey. Motion picture studies conducted at regular speeds provided information on cranial movements during the swallowing of prey. The morphology of the head was correlated with observed movements in an attempt to analyze the functional and adaptive implications of the jaw apparatus.

Journal of Morphology

4354335

10.1038/ISMEJ.2007.4

Microbial ecology meets electrochemistry: electricity-driven and driving communities

Bio-electrochemical systems (BESs) have recently emerged as an exciting technology. In a BES, bacteria interact with electrodes using electrons, which are either removed or supplied through an electrical circuit. The most-described type of BES is microbial fuel cells (MFCs), in which useful power is generated from electron donors as, for example, present in wastewater. This form of charge transport, known as extracellular electron transfer, was previously extensively described with respect to metals such as iron and manganese. The importance of these interactions in global biogeochemical cycles is essentially undisputed. A wide variety of bacteria can participate in extracellular electron transfer, and this phenomenon is far more widespread than previously thought. The use of BESs in diverse research projects is helping elucidate the mechanism by which bacteria shuttle electrons externally. New forms of interactions between bacteria have been discovered demonstrating how multiple populations within microbial communities can co-operate to achieve energy generation. New environmental processes that were difficult to observe or study previously can now be simulated and improved via BESs. Whereas pure culture studies make up the majority of the studies performed thus far, even greater contributions of BESs are expected to occur in natural environments and with mixed microbial communities. Owing to their versatility, unmatched level of control and capacity to sustain novel processes, BESs might well serve as the foundation of a new environmental biotechnology. While highlighting some of the major breakthroughs and addressing only recently obtained data, this review points out that despite rapid progress, many questions remain unanswered.

The ISME Journal

9163408

10.1242/JEB.004853

The magnetic compass of domestic chickens, Gallus gallus

SUMMARY By directional training, young domestic chickens have been shown to use a magnetic compass; the same method has now been used to analyse the functional characteristics and the physical principles underlying the chickens' magnetic compass. Tests in magnetic fields with different intensities revealed a functional window around the intensity of the local geomagnetic field, with this window extending further towards lower than higher intensities. Testing chickens under monochromatic 465 nm blue and 645 nm red light suggested a wavelength dependence, with orientation possible under blue but not under red light. Exposing chickens to an oscillating field of 1.566 MHz led to disorientation, identifying an underlying radical pair mechanism. Local anesthesia of the upper beak, where iron-rich structures have been described as potential magnetoreceptors, did not affect the performance, suggesting that these receptors are not involved in compass orientation. These findings show obvious parallels to the magnetic compass described for European robins, indicating that chickens and small passerines use the same type of magnetic compass mechanism. This suggests that the avian magnetic compass may have evolved in the common ancestor of all present-day birds to facilitate orientation within the home range.

The Journal of Experimental Biology

6188162

10.3354/CR005053

Adaptations of frogs to survive freezing

Five species of frogs from North A n ~ e n c a survive extensive freezing of their body fluids to temperatures as low as 8 ° C for periods lasting at least 2 wk. These frogs hibernate in leaf litter where subzero temperatures commonly occur during the winter. The onset of freezing triggers Liver glycogenolysis and the production of high concentrations of glucose or glycerol (to 100 X normal) that functions as a cryoprotectant against freezing Injury. Concomitantly the release of the latent heat of crystallization as body water freezes promotes the continued function of the cardiovascular system for many hours and serves to distribute glucose throughout the body. The water content of major organs is reduced by 50 U/:> or more during the first 24 h of freezing, wlth the water being relocated and frozen in other body spaces. Organ dehydration functions to concentrate cryoprotectant and to reduce mechanical damage by ice during freezing. As freezing progresses, breathing, heart beat , and most other v ~ t a l functions cease, but reanimation occurs ~ v ~ t h l n a few hours after thawing. The evolution of freeze tolerance in these animals illustrates the h~gh ly flexible capacities of frogs to adapt to stressful environments

Climate Research

5367027

10.1038/35070695

Acoustics: In a fly's ear

Organisms often identify the source of a sound by comparing the noises that arrive at the two ears. Using some interesting tricks, a minute fly has mastered this feat as accurately as humans.

Nature

135779387

10.1163/156856108X295491

Superhydrophobic Metallic Surfaces and Their Wetting Properties

Two-scaled polymer patterns possessing high roughness are produced using the hot-embossing technique and coating with chromium. After covering the rough polymer surface with this metal, the resulting surface demonstrates pronounced hydrophobic properties, with water drops having apparent contact angles as high as 150°. As revealed by SEM, the surface is patterned on two scales which is known to be an important condition for superhydrophobicity of inherently wettable surfaces. The modified Cassie–Baxter approach has been used for the present relief. The calculated values of the apparent contact angles agree with the observed ones. It is important to note that the apparent contact angles almost do not depend on the local contact angles.

Journal of Adhesion Science and Technology

32849349

10.1016/J.BONE.2007.07.013

Influence of physiological effort of growth and chemical composition on antler bone mechanical properties.

Antler is a good model to study bone biology both because it is accessible and because it grows and is shed every year. Previous studies have shown that chemical composition changes as the antler is grown, implying constraints in mineral availability and the physiological effort made to grow it. This study aimed at examining antler mechanical properties to assess whether they reflect physiological effort and whether they are associated with precise mineral bone composition rather than just ash content, which is usually the main factor affecting mechanical properties. We examined Young's modulus of elasticity (E), strength, and work to maximum load, as well as bone mineral composition, along the antler shaft. Then we compared trends between antlers from two populations: captive, well-fed, health-managed deer (n=15), and free-ranging deer with lower food quality and no health treatment (n=10). Greater E, strength and work were found for better fed and health managed deer. In addition, antler chemical composition of both populations differed in Na, Mg, K, Fe and Si, and marginally in Zn, but not in ash or Ca content. Significant and clear divergent trends in mechanical properties supporting greater physiological exhaustion in free-ranging deer were found for all mechanical variables. Detailed models showed that, in addition to ash content, independent factors extracted from principal component analyses on composition affected E and strength, but not work to maximum load. The results suggest that there is an association between bone chemical composition and mechanical properties independently of ash content.

Bone

43392332

10.1126/SCIENCE.212.4501.1397

Control of calcium carbonate nucleation and crystal growth by soluble matrx of oyster shell.

A calcium-binding soluble protein extracted from oyster shell suppresses calcium carbonate nucleation and decreases the rate of crystal growth in vitro. These findings suggest that soluble matrix may regulate shell growth.

Science

205018591

10.1038/35082144

Biomechanics: Turning the key on Drosophila audition

The genetic dissection of Drosophila audition is advancing considerably, but complementary studies are needed to unravel the chain of mechanosensory events that bring about hearing in the fly. Here we investigate the delicate biomechanics of the fly's minute antennal hearing organs and show that they look and work like a lock and key. Rotating in response to sound, the antenna's distal segment mechanically activates the auditory receptors — thereby 'unlocking' the mechanism of Drosophila audition.

Nature

1214294

10.1167/9.3.27

The pupils and optical systems of gecko eyes.

The nocturnal helmet gecko, Tarentola chazaliae, discriminates colors in dim moonlight when humans are color blind. The sensitivity of the helmet gecko eye has been calculated to be 350 times higher than human cone vision at the color vision threshold. The optics and the large cones of the gecko are important reasons why they can use color vision at low light intensities. Using photorefractometry and an adapted laboratory Hartmann-Shack wavefront sensor of high resolution, we also show that the optical system of the helmet gecko has distinct concentric zones of different refractive powers, a so-called multifocal optical system. The intraspecific variation is large but in most of the individuals studied the zones differed by 15 diopters. This is of the same magnitude as needed to focus light of the wavelength range to which gecko photoreceptors are most sensitive. We compare the optical system of the helmet gecko to that of the diurnal day gecko, Phelsuma madagascariensis grandis. The optical system of the day gecko shows no signs of distinct concentric zones and is thereby monofocal.

Journal of Vision

2140814

10.1016/J.COPBIO.2007.04.006

Obligate oil-degrading marine bacteria.

Over the past few years, a new and ecophysiologically unusual group of marine hydrocarbon-degrading bacteria - the obligate hydrocarbonoclastic bacteria (OHCB) - has been recognized and shown to play a significant role in the biological removal of petroleum hydrocarbons from polluted marine waters. The introduction of oil or oil constituents into seawater leads to successive blooms of a relatively limited number of indigenous marine bacterial genera--Alcanivorax, Marinobacter, Thallassolituus, Cycloclasticus, Oleispira and a few others (the OHCB)--which are present at low or undetectable levels before the polluting event. The types of OHCB that bloom depend on the latitude/temperature, salinity, redox and other prevailing physical-chemical factors. These blooms result in the rapid degradation of many oil constituents, a process that can be accelerated further by supplementation with limiting nutrients. Genome sequencing and functional genomic analysis of Alcanivorax borkumensis, the paradigm of OHCB, has provided significant insights into the genomic basis of the efficiency and versatility of its hydrocarbon utilization, the metabolic routes underlying its special hydrocarbon diet, and its ecological success. These and other studies have revealed the potential of OHCB for multiple biotechnological applications that include not only oil pollution mitigation, but also biopolymer production and biocatalysis.

Current Opinion in Biotechnology

10808242

10.1073/PNAS.0908205107

Subnanometer atomic force microscopy of peptide-mineral interactions links clustering and competition to acceleration and catastrophe.

In vitro observations have revealed major effects on the structure, growth, and composition of biomineral phases, including stabilization of amorphous precursors, acceleration and inhibition of kinetics, and alteration of impurity signatures. However, deciphering the mechanistic sources of these effects has been problematic due to a lack of tools to resolve molecular structures on mineral surfaces during growth. Here we report atomic force microscopy investigations using a system designed to maximize resolution while minimizing contact force. By imaging the growth of calcium-oxalate monohydrate under the influence of aspartic-rich peptides at single-molecule resolution, we reveal how the unique interactions of polypeptides with mineral surfaces lead to acceleration, inhibition, and switching of growth between two distinct states. Interaction with the positively charged face of calcium-oxalate monohydrate leads to formation of a peptide film, but the slow adsorption kinetics and gradual relaxation to a well-bound state result in time-dependent effects. These include a positive feedback between peptide adsorption and step inhibition described by a mathematical catastrophe that results in growth hysteresis, characterized by rapid switching from fast to near-zero growth rates for very small reductions in supersaturation. Interactions with the negatively charged face result in formation of peptide clusters that impede step advancement. The result is a competition between accelerated solute attachment and inhibition due to blocking of the steps by the clusters. The findings have implications for control of pathological mineralization and suggest artificial strategies for directing crystallization.

Proceedings of the National Academy of Sciences of the United States of America

11593924

10.1242/JEB.041434

Butterfly wing colors: glass scales of Graphium sarpedon cause polarized iridescence and enhance blue/green pigment coloration of the wing membrane

SUMMARY The wings of the swordtail butterfly Graphium sarpedon nipponum contain the bile pigment sarpedobilin, which causes blue/green colored wing patches. Locally the bile pigment is combined with the strongly blue-absorbing carotenoid lutein, resulting in green wing patches and thus improving camouflage. In the dorsal forewings, the colored patches lack the usual wing scales, but instead have bristles. We have found that on the ventral side most of these patches have very transparent scales that enhance, by reflection, the wing coloration when illuminated from the dorsal side. These glass scales furthermore create a strongly polarized iridescence when illuminated by obliquely incident light from the ventral side, presumably for intraspecific signaling. A few ventral forewing patches have diffusely scattering, white scales that also enhance the blue/green wing coloration when observed from the dorsal side.

The Journal of Experimental Biology

83870943

10.1016/0306-4565(85)90004-X

Body size and the control of heat exchange in alligators

Abstract 1. 1.|The ratio of rates of heating and cooling in American alligators in maximum at a body mass of about 5 kg. 2. 2.|There may be an optimum body size for the control of heat exchange by blood flow in American alligators.

Journal of Thermal Biology

206524044

10.1126/SCIENCE.1183310

Optimal Localization by Pointing Off Axis

Detection Versus Localization Active-sensing systems allow an animal some control over the information acquired from the environment. For example, echolocating bats are known to control many aspects of their sonar signal design. However, their sensory data-acquisition strategies are still not fully understood. Yovel et al. (p. 701) found that Egyptian fruit bats (Rousettus aegyptiacus) did not aim their sonar beams directly on target in a standard localization task. Instead, the bats pointed the main lobe of their sonar beam off-axis. Bats approaching the target emitted sounds to the left and right of its localization, in an alternating manner, so that the maximum slope of the change in intensity of the sonar beam was often positioned close to the target. This echolocation strategy is ideal for target localization but occurs at the cost of target detection. Echolocating Egyptian fruit bats do not center their sonar clicks on a target, thereby maximizing localization of the target. Is centering a stimulus in the field of view an optimal strategy to localize and track it? We demonstrated, through experimental and computational studies, that the answer is no. We trained echolocating Egyptian fruit bats to localize a target in complete darkness, and we measured the directional aim of their sonar clicks. The bats did not center the sonar beam on the target, but instead pointed it off axis, accurately directing the maximum slope (“edge”) of the beam onto the target. Information-theoretic calculations showed that using the maximum slope is optimal for localizing the target, at the cost of detection. We propose that the tradeoff between detection (optimized at stimulus peak) and localization (optimized at maximum slope) is fundamental to spatial localization and tracking accomplished through hearing, olfaction, and vision.

Science

23274596

10.1002/ECY.2008

Influence of neighboring plants on the dynamics of an ant-acacia protection mutualism.

Ant-plant protection symbioses, in which plants provide food and/or shelter for ants in exchange for protection from herbivory, are model systems for understanding the ecology of mutualism. While interactions between ants, host plants, and herbivores have been intensively studied, we know little about how plant-plant interactions influence the dynamics of these mutualisms, despite strong evidence that plants compete for resources, that hosting ants can be costly, and that host-plant provisioning to ants can therefore be constrained by resource availability. We used field experiments in a semiarid Kenyan savanna to examine interactions between the ant-plant Acacia drepanolobium, neighboring grasses, and two species of symbiotic acacia-ants with divergent behaviors: Crematogaster mimosae, an aggressive symbiont that imposes high costs to host trees via consumption of extrafloral nectar, and Tetraponera penzigi, a less-protective symbiont that imposes lower costs because it does not consume nectar. We hypothesized that by competing with acacias for resources, neighboring grasses (1) reduce hosts' ability to support costly C. mimosae, while having little or no effect on the ability of hosts to support low-cost T. penzigi, and (2) reduce sapling growth rates irrespective of ant occupant. We factorially manipulated the presence/absence of grasses and the identity of ant occupants on saplings and evaluated effects on colony survivorship and sapling growth rates over 40 weeks. Contrary to prediction, the high-cost/high-reward nectar-dependent mutualist C. mimosae had higher colony-survival rates on saplings with grass neighbors present. Grasses appear to have indirectly facilitated the survival of C. mimosae by reducing water stress on host plants; soils under saplings shaded by grasses had higher moisture content, and these saplings produced more active nectaries than grass-removal saplings. Consistent with prediction, survival of low-cost/low-reward T. penzigi did not differ significantly between grass-removal treatments. Saplings occupied by low-cost/low-reward T. penzigi grew 100% more on average than saplings occupied by high-cost/high-reward C. mimosae, demonstrating that mutualist-partner identity strongly and differentially influences demographic rates of young plants. In contrast, contrary to prediction, grass neighbors had no significant net impact on sapling growth rates. Our results suggest that neighboring plants can exert strong and counterintuitive effects on ant-plant protection symbioses, highlighting the need to integrate plant-plant interactions into our understanding of these mutualisms.

Ecology

22064311

10.1007/BF02861079

The aerodynamics of wind pollination

A number of morphologic features have evolved in evolutionarily divergent plant groups that appear to increase the efficiency of wind pollination. Among these features are the appearance of low density pollen grains, female ovulate organs that direct air currents carrying pollen toward stigmas or micropyles, and population structures with a high density of con-specifics. This paper reviews the aerodynamic theory, and the experimental and field data that are relevant to an understanding of the adaptive significance of these and other features of anemophily. Emphasis is placed on the mathematical description of the behavior of airflow patterns around ovulate organs. The efficiency of wind pollination is shown to be dictated principally by the vectoral properties of air currents created by and around ovulate organs and the physical properties of pollen that dictate their behavior as airborne particles.AbstraktEine Anzahl von morphologischen Kennzeichen, die Effizienz der Windpollination zu steigern scheinen, haben sich in evolutionär ausenandergehonden Pflanzengruppen entwickelt. Zu diesen Kennzeichen gehören die Erscheinung von Pollenkörnen von geringer Dichte, weiblichen Organen die pollentragende Luftströmungen zu den Stigmas oder Micropylen dirigieren, und Bevölkerungsstrukturen mit grosser Dichte von Con-specifics. Diese Abhandlung gibt einen überblick der aerodynamischen Theorie und der experimentelle Werte, die für das Verständnis der adaptiven Signifikanz dieser und anderer Kennzeichen der Windpollination von Bedeutung sind. Betont wird die mathematische Beschreibung des Verhaltens der Luftströmungen um die weiblichen Organe. Es wird gezeigt, dass die Effizienz der Windpollination hauptsächlich durch die vectoralen Eigenschaften der Luftströmungen die durch und um die weiblichen Organe entstehen, bestimmt wird, und durch die physischen Eigenschaften des Pollens, die sein Verhalten als luftgetragene Partikel diktieren.

Botanical Review

21049524

10.1111/J.1365-2915.2007.00682.X

Tissue and life‐stage distribution of a defensin gene in the Lone Star tick, Amblyomma americanum

Abstract The transcript sequence of the Amblyomma americanum Linnaeus (Acari: Ixodidae) defensin, termed amercin (amn), was ascertained and a 219‐bp amn coding region identified. The gene encodes a 72‐amino acid prepropeptide with a putative 37‐amino acid mature peptide. This gene shows little similarity to either of the defensins from Amblyomma hebraeum Koch, the only other Amblyomma species for which a defensin has been described. Sequence comparisons with other tick defensins reveal amn to be shorter (6 bp or 2 amino acids) than the Ixodes scapularis Linnaeus (Acari: Ixodidae) and Dermacentor variabilis (Say) (Acari: Ixodidae) defensin sequences. The amercin prepropeptide has 60.8% and 59.5% similarity with the I. scapularis and D. variabilis prepropeptides, respectively, whereas the mature amercin peptide has 73.7% and 71.1% similarity with the mature peptides of these ticks. Similarity with other tick defensins ranges from 42% to 71%. In A. americanum, defensin transcript was found in the midgut, fat body and salivary gland tissues, as well as in the haemocytes. Defensin transcript was also present in early‐stage eggs (less than 48 h old), late‐stage eggs (approximately 2 weeks old), larvae and nymphs of A. americanum and I. scapularis, both of which are vector‐competent for Borrelia spirochetes.

Medical and Veterinary Entomology

18607960

10.1093/AOB/MCP251

Arbuscular mycorrhizal fungi in alleviation of salt stress: a review.

BACKGROUND Salt stress has become a major threat to plant growth and productivity. Arbuscular mycorrhizal fungi colonize plant root systems and modulate plant growth in various ways. SCOPE This review addresses the significance of arbuscular mycorrhiza in alleviation of salt stress and their beneficial effects on plant growth and productivity. It also focuses on recent progress in unravelling biochemical, physiological and molecular mechanisms in mycorrhizal plants to alleviate salt stress. CONCLUSIONS The role of arbuscular mycorrhizal fungi in alleviating salt stress is well documented. This paper reviews the mechanisms arbuscular mycorrhizal fungi employ to enhance the salt tolerance of host plants such as enhanced nutrient acquisition (P, N, Mg and Ca), maintenance of the K(+) : Na(+) ratio, biochemical changes (accumulation of proline, betaines, polyamines, carbohydrates and antioxidants), physiological changes (photosynthetic efficiency, relative permeability, water status, abscissic acid accumulation, nodulation and nitrogen fixation), molecular changes (the expression of genes: PIP, Na(+)/H(+) antiporters, Lsnced, Lslea and LsP5CS) and ultra-structural changes. Theis review identifies certain lesser explored areas such as molecular and ultra-structural changes where further research is needed for better understanding of symbiosis with reference to salt stress for optimum usage of this technology in the field on a large scale. This review paper gives useful benchmark information for the development and prioritization of future research programmes.

Annals of Botany

53151822

10.1016/J.ANBEHAV.2015.09.019

New insights into the huddling dynamics of emperor penguins

Social thermoregulation is a cooperative strategy in which animals actively aggregate to benefit from the warmth of conspecifics in response to low ambient temperatures. Emperor penguins, Aptenodytes forsteri , use this behaviour to ensure their survival and reproduction during the Antarctic winter. An emperor penguin colony consists of a dynamic mosaic of compact zones, the so-called huddles, included in a looser network of individuals. To maximize energy savings, birds should adjust their huddling behaviour according to environmental conditions. Here, we examined the dynamics of emperor penguin aggregations, based on photo and video records, in relation to climatic factors. Environmental temperature, wind and solar radiation were the main factors contributing to huddle formation. The analysis of individual movements showed that birds originating from loose aggregations continually joined huddles. Sometimes, a small number of birds induced a movement that propagated to the entire huddle, causing its breakup within 2 min and releasing birds, which then integrated into looser aggregations. Different parts of the colony therefore appeared to continually exchange individuals in response to environmental conditions. A likely explanation is that individuals in need of warmth join huddles, whereas individuals seeking to dissipate heat break huddles apart. The regular growth and decay of huddles operates as pulses through which birds gain, conserve or lose heat. Originally proposed to account for reducing energy expenditure, the concept of social thermoregulation appears to cover a highly dynamic phenomenon that fulfils a genuine regulatory function in emperor penguins.

Animal Behaviour

38924856

10.1088/0953-8984/17/9/021

Towards ultrahydrophobic surfaces : a biomimetic approach

We report on efforts to mimic the wetting behaviour of surfaces or leaves of certain plants, which are rendered ultrahydrophobic through a dense layer of hairs grown on top of the leaf. We use a simple moulding approach to obtain elastic hydrophilic hydrogel networks with pillar structures that may serve as model systems for such hairy surfaces. In order to generate such structures, we first generate either a steel master or directly use a lady's mantle leaf. Second, the master is moulded against a silicone to yield an elastomer, which is a negative of the hairy surface. A subsequent radical polymerization in the negative leads to the formation of an elastic hydrogel even for the very high aspect ratios characteristic of the natural system. The results of some preliminary contact angle measurements on the obtained structures are discussed.

Journal of Physics: Condensed Matter

86826415

10.1111/J.0908-8857.2008.04299.X

Bill sweeping in spoonbills Platalea: no evidence for an effective suction force at the tip

We analysed the hypothesis of Weihs and Katzir (1994) that feeding spoonbills use their broad bills by sweeping it through the water to shed a vortex. This would result in a hydrodynamic suction on the bottom for catching prey immediately or during the next sweep besides providing some extra benefits. The basic assumptions appear to be erroneous. (1) A spoonbill does not mainly feed on small, benthic invertebrates, but mainly on nekton such as fish and shrimps. (2) The inner surface of the upper mandible of a spoonbill is not concave but convex. (3) During feeding, a spoonbill does not keep its bill tip close to the bottom independent of the water depth. The outcomes of the tests supporting the hypothesis do not hold and the suggested benefits are dubious. Therefore, we reject the hypothesis and the claim that the bill of a spoonbill is used as a hydrofoil. The discussed paper tried to give an explanation of the behaviour of a bird with the help of hydrodynamic formulae. The fundamental mistake in the paper is that the use of the formulae is based on wrong assumptions concerning the food of the bird, its feeding behaviour as well as its anatomical details. The tests with a bird kept in captivity suggesting a proof of the rightness of the hypothesis lack a proper connection to the situation in the wild. Spoonbills (Aves: Ciconiiformes: Threskiornithidae, genus Platalea) are large wading birds characterised by their extremely flattened bills that are widened in the distal parts. The six species are very similar in shape and behaviour, mainly differing in size, colour of legs, bills and other bare parts, and in distribution (Matheu and del Hoyo 1992). They feed tactilely by walking in shallow

Journal of Avian Biology

6418841

10.1371/JOURNAL.PONE.0152325

Total Internal Reflection Accounts for the Bright Color of the Saharan Silver Ant

The Saharan silver ant Cataglyphis bombycina is one of the terrestrial living organisms best adapted to tolerate high temperatures. It has recently been shown that the hairs covering the ant’s dorsal body part are responsible for its silvery appearance. The hairs have a triangular cross-section with two corrugated surfaces allowing a high optical reflection in the visible and near-infrared (NIR) range of the spectrum while maximizing heat emissivity in the mid-infrared (MIR). Those two effects account for remarkable thermoregulatory properties, enabling the ant to maintain a lower thermal steady state and to cope with the high temperature of its natural habitat. In this paper, we further investigate how geometrical optical and high reflection properties account for the bright silver color of C. bombycina. Using optical ray-tracing models and attenuated total reflection (ATR) experiments, we show that, for a large range of incidence angles, total internal reflection (TIR) conditions are satisfied on the basal face of each hair for light entering and exiting through its upper faces. The reflection properties of the hairs are further enhanced by the presence of the corrugated surface, giving them an almost total specular reflectance for most incidence angles. We also show that hairs provide an almost 10-fold increase in light reflection, and we confirm experimentally that they are responsible for a lower internal body temperature under incident sunlight. Overall, this study improves our understanding of the optical mechanisms responsible for the silver color of C. bombycina and the remarkable thermoregulatory properties of the hair coat covering the ant’s body.

PLOS ONE

56229153

10.3844/AJNSP.2011.112.121

Factors Affecting the Geometry of Silver Nanoparticles Synthesis in Chrysosporium Tropicum and Fusarium Oxysporum

Problem statement: Biosynthesis of nanoparticles using fungal cells is a novel approach to develop biotechnological possess such as bioleaching and bioremediation. In the present study, an effort was made to investigate the effect of physio-chemical parameters on the silver nanoparticle formation with the fungus Chrysosporium tropicum Carmichael and Fusarium oxysporum Schltdl. Approach: The possibilities to manipulating the geometry of silver nanoparticles by altering the key growth parameters such as pH, temperature, concentrations and time have been explored. The effect of AgNO3 with the cell free extract of fungi and time, temperature, pH with the formation of silver has also been investigated. The presence of nanosilver has been carried out with the Micro-scan reader and has been confirmed by X-Rays Diffractometer (XRD). The micrographs of the silver nanoparticles have been evaluated through the Transmission Electron Microscope (TEM) and confirmed by Scanning Electron Microscope (SEM). The effect of concentrations with response to time, temperature and pH has studied with the help of Micro-scan reader and their microstructure analyzed by TEM and SEM. Results: It was observed that fungus C. tropicum and F. oxysporum Schltdl significantly activate the extra-cellular production of silver nanoparticles. The different sized and spherical shaped nanoparticles have been formed in different strains. With the increase in concentration, the absorbance increased with response to time (24-120h) and temperature. Significantly, the pH was found decreasing with the increase of absorbance. Conclusion: We presume that these changes initiate new geometry of nanosilver in the cell free solutions. These different shaped, sized and geometry of nanoparticles can be used in the field of medicine for drug formation and diseases diagnosis.

Current Research in Nanotechnology

15554570

10.1002/AJPA.21096

The influence of fallback foods on great ape tooth enamel.

Lucas and colleagues recently proposed a model based on fracture and deformation concepts to describe how mammalian tooth enamel may be adapted to the mechanical demands of diet (Lucas et al.: Bioessays 30 2008 374-385). Here we review the applicability of that model by examining existing data on the food mechanical properties and enamel morphology of great apes (Pan, Pongo, and Gorilla). Particular attention is paid to whether the consumption of fallback foods is likely to play a key role in influencing great ape enamel morphology. Our results suggest that this is indeed the case. We also consider the implications of this conclusion on the evolution of the dentition of extinct hominins.

American Journal of Physical Anthropology

24915869

10.1073/PNAS.0705459104

A honey bee odorant receptor for the queen substance 9-oxo-2-decenoic acid

By using a functional genomics approach, we have identified a honey bee [Apis mellifera (Am)] odorant receptor (Or) for the queen substance 9-oxo-2-decenoic acid (9-ODA). Honey bees live in large eusocial colonies in which a single queen is responsible for reproduction, several thousand sterile female worker bees complete a myriad of tasks to maintain the colony, and several hundred male drones exist only to mate. The “queen substance” [also termed the queen retinue pheromone (QRP)] is an eight-component pheromone that maintains the queen's dominance in the colony. The main component, 9-ODA, acts as a releaser pheromone by attracting workers to the queen and as a primer pheromone by physiologically inhibiting worker ovary development; it also acts as a sex pheromone, attracting drones during mating flights. However, the extent to which social and sexual chemical messages are shared remains unresolved. By using a custom chemosensory-specific microarray and qPCR, we identified four candidate sex pheromone Ors (AmOr10, -11, -18, and -170) from the honey bee genome based on their biased expression in drone antennae. We assayed the pheromone responsiveness of these receptors by using Xenopus oocytes and electrophysiology. AmOr11 responded specifically to 9-ODA (EC50 = 280 ± 31 nM) and not to any of the other seven QRP components, other social pheromones, or floral odors. We did not observe any responses of the other three Ors to any of the eight QRP pheromone components, suggesting 9-ODA is the only QRP component that also acts as a long-distance sex pheromone.

Proceedings of the National Academy of Sciences of the United States of America

136889539

10.1016/J.CARBON.2010.10.048

Super black and ultrathin amorphous carbon film inspired by anti-reflection architecture in butterfly wing

Abstract An ultrathin and super black amorphous carbon (a-C) film has been fabricated by borrowing the inverse V-type anti-reflection nano-architecture from the black wings of butterfly Ornithoptera goliath through vacuum sintering process. The biomimetic a-C film shows good optical absorption (99%) at low reflectance (

Carbon

34342262

10.1126/SCIENCE.219.4581.185

Spider Web Protection Through Visual Advertisement: Role of the Stabilimentum

The conspicuous white silken adornments known as stabilimenta, which are commonly found in the orb webs of some spiders, appear to be protective devices that warn birds of the presence of webs in their flight path. Webs endowed with artificial equivalents of stabilimenta tended to survive intact the early morning period when birds are on the wing; unmarked webs showed a high incidence of destruction.

Science

4280030

10.1038/238160A0

Physiological Colour Change in the Hercules Beetle

THE Hercules beetle, Dynastes Hercules L., can change the colour of its elytra—horny fore-wings—from black to greenish yellow and back again to black all within a few minutes. It does this in a way previously unknown among insects. Apart from the reversible migrations of pigment granules in the iris cells, physiological or rapidly reversible colour changes are very rare in insects1–4. Among beetles, Coptocyclia5, Aspidomorpha, and many other Cassidinae can change the colour of their elytra by varying the amount of water in the cuticle and thereby the thickness of the thin films responsible for the interference colours.

Nature

17164379

10.1016/J.CUB.2015.11.057

The Venus Flytrap Dionaea muscipula Counts Prey-Induced Action Potentials to Induce Sodium Uptake

Summary Carnivorous plants, such as the Venus flytrap (Dionaea muscipula), depend on an animal diet when grown in nutrient-poor soils. When an insect visits the trap and tilts the mechanosensors on the inner surface, action potentials (APs) are fired. After a moving object elicits two APs, the trap snaps shut, encaging the victim. Panicking preys repeatedly touch the trigger hairs over the subsequent hours, leading to a hermetically closed trap, which via the gland-based endocrine system is flooded by a prey-decomposing acidic enzyme cocktail. Here, we asked the question as to how many times trigger hairs have to be stimulated (e.g., now many APs are required) for the flytrap to recognize an encaged object as potential food, thus making it worthwhile activating the glands. By applying a series of trigger-hair stimulations, we found that the touch hormone jasmonic acid (JA) signaling pathway is activated after the second stimulus, while more than three APs are required to trigger an expression of genes encoding prey-degrading hydrolases, and that this expression is proportional to the number of mechanical stimulations. A decomposing animal contains a sodium load, and we have found that these sodium ions enter the capture organ via glands. We identified a flytrap sodium channel DmHKT1 as responsible for this sodium acquisition, with the number of transcripts expressed being dependent on the number of mechano-electric stimulations. Hence, the number of APs a victim triggers while trying to break out of the trap identifies the moving prey as a struggling Na+-rich animal and nutrition for the plant. Video Abstract

Current Biology

85045069

10.1051/APIDO:19920505

Pre-copulatory courtship behavior in a solitary bee, Nomia triangulifera Vachal (Hymenoptera : Halictidae)

Comportement de cour precopulatoire chez une abeille solitaire, Nomia triangulifera Vachal (Hymenoptera, Halictidae). L'abeille terricole, Nomia triangulifera, presente un comportement de cour complexe avant et pendant l'accouplement. Le comportement d'accouplement a ete etudie sur de grosses aggregations dans une ferme du Nord-Est du Kansas, ou les abeilles nidifient depuis de nombreuses annees. En 1989 et 1990, on a capture des abeilles qui emergeaient afin de determiner la phenologie de l'emergence et d'estimer le sex-ratio journalier d'accouplement (nombre de mâles presents/nombre de femelles receptives)

Apidologie

33080223

10.1242/JEB.02682

Adhesive recruitment by the viscous capture threads of araneoid orb-weaving spiders

SUMMARY The sticky prey capture threads of orb-webs are critical to web performance. By retaining insects that strike the web, these spirally arrayed threads allow a spider time to locate and subdue prey. The viscous capture threads spun by modern orb-weaving spiders of the Araneoidea clade replaced the dry, fuzzy cribellar capture threads of the Deinopoidea and feature regularly spaced moist, adhesive droplets. The stickiness of a cribellar thread is limited by its tendency to peel from a surface after the adhesion generated at the edges of contact is exceeded. In this study we test the hypothesis that viscous thread overcomes this limitation by implementing a suspension bridge mechanism (SBM) that recruits the adhesion of multiple thread droplets. We do so by using contact plates of four widths to measure the stickiness of six species' viscous threads whose profiles range from small, closely spaced droplets to large, widely spaced droplets. The increased stickiness registered by an increased number of thread droplets supports the operation of a SBM. However, the accompanying decrease in mean per droplet adhesion shows that droplets interior to the edges of thread contact contribute successively less adhesion. Models developed from these data suggest that the suspension bridge mechanism is limited to a span of approximately 12 droplets.

The Journal of Experimental Biology

83968430

10.1111/J.1600-0706.2011.20179.X

Parasites and mutualism function: measuring enemy-free space in a fig–pollinator symbiosis

Mutualisms involve cooperation between species and underpin several ecosystem functions. However, there is also conflict between mutualists, because their interests are not perfectly aligned. In addition, most mutualisms are exploited by parasites. Here, we study the interplay between cooperation, conflict and parasitism in the mutualism between fig trees and their pollinator wasps. Conflict occurs because each fig ovary can nurture either one seed or one pollinator offspring and, while fig trees benefit directly from seeds and pollinator offspring (pollen vectors), pollinators only benefit directly from pollinator offspring. The mechanism(s) of conflict resolution is debated, but must explain the widespread observation that pollinators develop in inner, and seeds in outer, layers of fig flowers. We recently suggested a role for non-pollinating figs wasps (NPFWs) that are natural enemies or competitors of the pollinators and lay their eggs through the fig wall. Most NPFW offspring develop in outer and middle layer flowers, suggesting that inner flowers provide enemy-free space for pollinator offspring. Here, we test the hypothesis that NPFWs cannot reach inner flowers, by measuring wasp and fig morphology at the species-specific times of NPFW attack in the field. We found that three species of Sycoscapter and Philotrypesis wasps that parasitise pollinators could reach 34–73%, 75–92% and 82–97% of fig ovaries, respectively. Meanwhile, Eukobelea and Pseudidarnes gall-formers, despite having shorter ovipositors, can access almost all fig flowers (93–99% and 100%), because they attack smaller (younger) fig fruits. Our mechanistic results from ovipositing wasps support spatial patterns of wasp offspring segregation within figs to suggest that inner ovules provide enemy-free-space for pollinators. This may contribute to mutualism stability by helping select for pollinators to avoid laying eggs where they are likely to be parasitised. These outer flowers then remain free to develop as seeds, promoting mutualism persistence.

Oikos

28598530

10.1086/342819

Sensory Trap as the Mechanism of Sexual Selection in a Damselfly Genitalic Trait (Insecta: Calopterygidae)

During copulation, males of some calopterygid damselfly species displace the sperm stored in the spermatheca: the male genital appendages enter into the spermathecal ducts and physically remove sperm. In Calopteryx haemorrhoidalis, the genital appendages are too wide to penetrate the spermathecae, but males use a different mechanism in which the aedeagus stimulates the vaginal sensilla that control spermathecal sperm release. Since these sensilla are used during egg fertilization and oviposition, it was hypothesized that this function evolved before the male stimulatory ability. I investigated this using Hetaerina cruentata, a species whose position in the Calopterygidae phylogeny is more basal than Calopteryx. Given this position and having determined that males of this species are not able to displace sperm of their conspecific females during copulation, it was expected that H. cruentata females would eject sperm when stimulated with the aedeagi of C. haemorrhoidalis but not when stimulated with the aedeagi of their conspecifics. This prediction was confirmed. In order to investigate the widespread nature of this result, some other Calopteryx species—Calopteryx xanthostoma and Calopteryx virgo—were investigated. The results were similar to those of H. cruentata: conspecific males were unable to stimulate their females, but females ejected sperm when stimulated with C. haemorrhoidalis aedeagi. Morphometric analysis suggests that the mechanistic explanation for the stimulatory ability of C. haemorrhoidalis genitalia is that the aedeagal region that makes contact with the vaginal sensilla is wider in C. haemorrhoidalis than in the other species. These results suggest that the sensory “bias” shown and shared by H. cruentata, Calopteryx splendens, C. virgo, and C. haemorrhoidalis females represents an ancestral condition and that the male stimulatory ability is absent in the evolutionary history of the clade. These pieces of evidence as well as another one presented elsewhere, which indicates that C. haemorrhoidalis males vary in their stimulatory ability, constitute the three criteria for a case of sexual selection via exploitation of a female sensory bias. These results also provide support to the sensory trap hypothesis that indicates that the female bias—in this case, egg fertilization and oviposition—evolved in a context different from sexual selection. Considering that the male genital appendages responsible for physically removing spermathecal sperm in other calopterygids are present in C. haemorrhoidalis, I suggest that males were once able to displace spermathecal sperm physically. Such ability may have been later impeded by a reduction in size of the spermathecal ducts. Possibly, one of the latest events in this sequence is the male’s stimulatory ability. This hypothetical series of events suggests a coevolutionary scenario in which the central actor is the sperm stored in the spermathecae.

The American Naturalist

9896261

10.1371/JOURNAL.PONE.0020260

Coordinated Movements Prevent Jamming in an Emperor Penguin Huddle

For Emperor penguins (Aptenodytes forsteri), huddling is the key to survival during the Antarctic winter. Penguins in a huddle are packed so tightly that individual movements become impossible, reminiscent of a jamming transition in compacted colloids. It is crucial, however, that the huddle structure is continuously reorganized to give each penguin a chance to spend sufficient time inside the huddle, compared with time spent on the periphery. Here we show that Emperor penguins move collectively in a highly coordinated manner to ensure mobility while at the same time keeping the huddle packed. Every 30–60 seconds, all penguins make small steps that travel as a wave through the entire huddle. Over time, these small movements lead to large-scale reorganization of the huddle. Our data show that the dynamics of penguin huddling is governed by intermittency and approach to kinetic arrest in striking analogy with inert non-equilibrium systems, including soft glasses and colloids.

PLOS ONE

1755540

10.1098/RSBL.2004.0289

Carotenoids need structural colours to shine

The bright colours of feathers are among the most striking displays in nature and are frequently used as sexual signals. Feathers can be coloured by pigments or by ordered tissue, and these mechanisms have traditionally been treated as distinct modes of display. Here we show that some yellow plumage colour is created both by reflection of light from white structural tissue and absorption of light by carotenoids. Thus, structural components of feathers contribute substantially to yellow ‘carotenoid’ displays, but the effect of variation in structural components on variation in colour displays is, to our knowledge, unstudied. The presence of structural colour in some carotenoid-based colour displays will have to be considered in studies of colour signalling.

Biology Letters

51686330

10.1063/1.1688341

Leading-edge tubercles delay stall on humpback whale (Megaptera novaeangliae) flippers

The humpback whale (Megaptera novaeangliae) is exceptional among the baleen whales in its ability to undertake acrobatic underwater maneuvers to catch prey. In order to execute these banking and turning maneuvers, humpback whales utilize extremely mobile flippers. The humpback whale flipper is unique because of the presence of large protuberances or tubercles located on the leading edge which gives this surface a scalloped appearance. We show, through wind tunnel measurements, that the addition of leading-edge tubercles to a scale model of an idealized humpback whale flipper delays the stall angle by approximately 40%, while increasing lift and decreasing drag.

Physics of Fluids

18850707

10.1242/JEB.02792

Running in ostriches (Struthio camelus): three-dimensional joint axes alignment and joint kinematics

SUMMARY Although locomotor kinematics in walking and running birds have been examined in studies exploring many biological aspects of bipedalism, these studies have been largely limited to two-dimensional analyses. Incorporating a five-segment, 17 degree-of-freedom (d.f.) kinematic model of the ostrich hind limb developed from anatomical specimens, we quantified the three-dimensional (3-D) joint axis alignment and joint kinematics during running (at ∼3.3 m s–1) in the largest avian biped, the ostrich. Our analysis revealed that the majority of the segment motion during running in the ostrich occurs in flexion/extension. Importantly, however, the alignment of the average flexion/extension helical axes of the knee and ankle are rotated externally to the direction of travel (37° and 21°, respectively) so that pure flexion and extension at the knee will act to adduct and adbuct the tibiotarsus relative to the plane of movement, and pure flexion and extension at the ankle will act to abduct and adduct the tarsometatarsus relative to the plane of movement. This feature of the limb anatomy appears to provide the major lateral (non-sagittal) displacement of the lower limb necessary for steering the swinging limb clear of the stance limb and replaces what would otherwise require greater adduction/abduction and/or internal/external rotation, allowing for less complex joints, musculoskeletal geometry and neuromuscular control. Significant rotation about the joints' non-flexion/extension axes nevertheless occurs over the running stride. In particular, hip abduction and knee internal/external and varus/valgus motion may further facilitate limb clearance during the swing phase, and substantial non-flexion/extension movement at the knee is also observed during stance. Measurement of 3-D segment and joint motion in birds will be aided by the use of functionally determined axes of rotation rather than assumed axes, proving important when interpreting the biomechanics and motor control of avian bipedalism.

The Journal of Experimental Biology

16454013

10.1016/S1672-6529(07)60015-8

Biomimetics of campaniform sensilla: Measuring strain from the deformation of holes

We present a bio-inspired strategy for designing embedded strain sensors in space structures. In insects, the campaniform sensillum is a hole extending through the cuticle arranged such that its shape changes in response to loads. The shape change is rotated through 90° by the suspension of a bell-shaped cap whose deflection is detected by a cell beneath the cuticle. It can be sensitive to displacements of the order of 1 nm. The essential morphology, a hole formed in a plate of fibrous composite material, was modelled by Skordos et al. who showed that global deformation of the plate (which can be flat, curved or a tube) induces higher local deformation of the hole due to its locally higher compliance. Further developments reported here show that this approach can be applied to groups of holes relative to their orientation.The morphology of the sensillum in insects suggests that greater sensitivity can be achieved by arranging several holes in a regular pattern; that if the hole is oval it can be “aimed” to sense specific strain directions; and that either by controlling the shape of the hole or its relationship with other holes it can have a tuned response to dynamic strains.We investigate space applications in which novel bio-inspired strain sensors could successfully be used.

Journal of Bionic Engineering

18094778

10.1098/RSIF.2014.0541

Three-dimensional flow and lift characteristics of a hovering ruby-throated hummingbird

A three-dimensional computational fluid dynamics simulation is performed for a ruby-throated hummingbird (Archilochus colubris) in hovering flight. Realistic wing kinematics are adopted in the numerical model by reconstructing the wing motion from high-speed imaging data of the bird. Lift history and the three-dimensional flow pattern around the wing in full stroke cycles are captured in the simulation. Significant asymmetry is observed for lift production within a stroke cycle. In particular, the downstroke generates about 2.5 times as much vertical force as the upstroke, a result that confirms the estimate based on the measurement of the circulation in a previous experimental study. Associated with lift production is the similar power imbalance between the two half strokes. Further analysis shows that in addition to the angle of attack, wing velocity and surface area, drag-based force and wing–wake interaction also contribute significantly to the lift asymmetry. Though the wing–wake interaction could be beneficial for lift enhancement, the isolated stroke simulation shows that this benefit is buried by other opposing effects, e.g. presence of downwash. The leading-edge vortex is stable during the downstroke but may shed during the upstroke. Finally, the full-body simulation result shows that the effects of wing–wing interaction and wing–body interaction are small.

Journal of the Royal Society Interface

2864513

10.1073/PNAS.1106288108

Algal ice-binding proteins change the structure of sea ice

Krembs et al. (1) reported that extracellular polymeric substances (EPS) produced by a sea ice diatom, Melosira, created convoluted ice-pore morphologies in sea ice, potentially increasing its habitability and primary productivity. The activity was reduced by heat treatment and glycosidase treatments, suggesting that a glycoprotein was involved. Based on our previous work (2), it is very likely that the active substance is an ice-binding protein (IBP).

Proceedings of the National Academy of Sciences of the United States of America

35498558

10.1242/JEB.054585

Hydraulic leg extension is not necessarily the main drive in large spiders

SUMMARY Unlike most other arthropods, spiders have no extensor muscles in major leg joints. Therefore, hydraulic pressure generated in the prosoma provides leg extension. For decades, this mechanism was held responsible for the generation of the majority of the ground reaction forces, particularly in the hind legs. During propulsion, the front leg pairs must shorten whereas the hind legs have to be extended. Assuming that hind legs are essentially driven by hydraulics, their force vectors must pass the leg joints ventrally. However, at least in accelerated escape manoeuvres, we show here for the large cursorial spider species Ancylometes concolor that these force vectors, when projected into the leg plane, pass all leg joints dorsally. This indicates a reduced impact of the hydraulic mechanism on the generation of ground reaction forces. Although hydraulic leg extension still modulates their direction, the observed steep force vectors at the hind legs indicate a strong activity of flexors in the proximal joint complex that push the legs against the substrate. Consequently, the muscular mechanisms are dominant at least in the hind legs of large spiders.

The Journal of Experimental Biology

1564602

10.1098/RSIF.2008.0457

Hydrodynamics of sailing of the Portuguese man-of-war Physalia physalis

Physalia physalis, commonly known as the Portuguese man-of-war (PMW), is a peculiar looking colony of specialized polyps. The most conspicuous members of this colony are the gas-filled sail-like float and the long tentacles, budding asymmetrically beneath the float. This study addresses the sailing of the PMW, and, in particular, the hydrodynamics of its trailing tentacles, the interaction between the tentacles and the float and the actual sailing performance. This paper attempts to provide answers for two of the many open questions concerning P. physalis: why does it need a sail? and how does it harness the sail?

Journal of the Royal Society Interface

5423405

10.1371/JOURNAL.PONE.0158277

Shooting Mechanisms in Nature: A Systematic Review

Background In nature, shooting mechanisms are used for a variety of purposes, including prey capture, defense, and reproduction. This review offers insight into the working principles of shooting mechanisms in fungi, plants, and animals in the light of the specific functional demands that these mechanisms fulfill. Methods We systematically searched the literature using Scopus and Web of Knowledge to retrieve articles about solid projectiles that either are produced in the body of the organism or belong to the body and undergo a ballistic phase. The shooting mechanisms were categorized based on the energy management prior to and during shooting. Results Shooting mechanisms were identified with projectile masses ranging from 1·10−9 mg in spores of the fungal phyla Ascomycota and Zygomycota to approximately 10,300 mg for the ballistic tongue of the toad Bufo alvarius. The energy for shooting is generated through osmosis in fungi, plants, and animals or muscle contraction in animals. Osmosis can be induced by water condensation on the system (in fungi), or water absorption in the system (reaching critical pressures up to 15.4 atmospheres; observed in fungi, plants, and animals), or water evaporation from the system (reaching up to −197 atmospheres; observed in plants and fungi). The generated energy is stored as elastic (potential) energy in cell walls in fungi and plants and in elastic structures in animals, with two exceptions: (1) in the momentum catapult of Basidiomycota the energy is stored in a stalk (hilum) by compression of the spore and droplets and (2) in Sphagnum energy is mainly stored in compressed air. Finally, the stored energy is transformed into kinetic energy of the projectile using a catapult mechanism delivering up to 4,137 J/kg in the osmotic shooting mechanism in cnidarians and 1,269 J/kg in the muscle-powered appendage strike of the mantis shrimp Odontodactylus scyllarus. The launch accelerations range from 6.6g in the frog Rana pipiens to 5,413,000g in cnidarians, the launch velocities from 0.1 m/s in the fungal phylum Basidiomycota to 237 m/s in the mulberry Morus alba, and the launch distances from a few thousands of a millimeter in Basidiomycota to 60 m in the rainforest tree Tetraberlinia moreliana. The mass-specific power outputs range from 0.28 W/kg in the water evaporation mechanism in Basidiomycota to 1.97·109 W/kg in cnidarians using water absorption as energy source. Discussion and conclusions The magnitude of accelerations involved in shooting is generally scale-dependent with the smaller the systems, discharging the microscale projectiles, generating the highest accelerations. The mass-specific power output is also scale dependent, with smaller mechanisms being able to release the energy for shooting faster than larger mechanisms, whereas the mass-specific work delivered by the shooting mechanism is mostly independent of the scale of the shooting mechanism. Higher mass-specific work-values are observed in osmosis-powered shooting mechanisms (≤ 4,137 J/kg) when compared to muscle-powered mechanisms (≤ 1,269 J/kg). The achieved launch parameters acceleration, velocity, and distance, as well as the associated delivered power output and work, thus depend on the working principle and scale of the shooting mechanism.

PLOS ONE

6890187

10.1007/BF00615085

Striking of underwater prey by a reef heron,Egretta gularis schistacea

SummaryThe ability of a piscivorous bird, the western reef heron,Egretta gularis schistacea, to cope with light refraction at the air/water interface was investigated. The heron's capture rate of small stationary underwater prey from a variety of angles was high, indicating an ability to correct for refraction. Two distinct phases were described during head movement: i) ‘Pre-strike’ (mean path angle 60° to the vertical, mean velocity 52 cm/s). ii) ‘Strike’ (mean path angle 33°, mean velocity 270 cm/s). When prey was unsubmerged the two phases were less distinct (‘pre-strike’ 47°, 62 cm/s; ‘strike’ 42°, 154 cm/s). The point of change between phases (STR) was assumed to be the point at which corrections for refraction were performed. Calculated disparities between real and apparent prey positions at STR may reach 10 cm. At STR, highly significant correlations were found between i) the heron's eye height above the water, and prey depth, ii) the apparent prey depth and real prey depth. A model is presented to explain the heron's manner of correcting for light refraction.

Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology

27088981

10.1126/SCIENCE.1103114

Periodical Cicadas as Resource Pulses in North American Forests

Resource pulses are occasional events of ephemeral resource superabundance that occur in many ecosystems. Aboveground consumers in diverse communities often respond strongly to resource pulses, but few studies have investigated the belowground consequences of resource pulses in natural ecosystems. This study shows that resource pulses of 17-year periodical cicadas (Magicicada spp.) directly increase microbial biomass and nitrogen availability in forest soils, with indirect effects on growth and reproduction in forest plants. These findings suggest that pulses of periodical cicadas create “bottom-up cascades,” resulting in strong and reciprocal links between the aboveground and belowground components of a North American forest ecosystem.

Science

137882492

10.1007/BF03220386

The insect exoskeleton: A natural structural composite

Through untold centuries of evolutionary development, the insect exoskeleton has become a highly optimized structure suited to a variety of demanding duties. Microscopic examination of the bessbeetle cuticle indicates that it is a composite consisting of layered plies having fiber orientations that alternate in a dual helicoidal pattern. Further, the geometry and size of the reinforcing fibers varies with the position of the ply. Several interesting structures discovered in the insect exoskeleton may provide fodder for new ideas on composite joining, ply orientation and fiber size and geometry.

JOM

178082114

10.1126/SCIENCE.1123995

Artificial Muscle Begins to Breathe

In robots, the power source is usually distant from the actual moving parts, which can be inefficient. One solution is to provide power locally, as in real muscles, by incorporating fuel cell technology directly into artificial muscles.

Science

96549298

10.1039/C0EE00578A

Natural light harvesting: principles and environmental trends

Light harvesting in photosynthetic organisms is largely an efficient process. The first steps of the light phase of photosynthesis, capture of light quanta and primary charge separation processes are particularly well-tuned. In plants, these primary events that take place within the photosystems possess remarkable quantum efficiency, reaching 80% and 100% in photosystems II and I respectively. This paper presents a view on the organisation of a natural light harvesting machine—the antenna of the photosystem II of higher plants. It explains the key principles of biological antenna design and the strategies of adaptation to light environment which have evolved over millions of years. This article argues that the high efficiency of the light harvesting antenna and its control are intimately interconnected owing to the molecular design of the pigment–proteins it is built of, enabling high pigment density combined with the long excited-state lifetime. The protein plays the role of a programmed solvent, accommodating high quantities of pigments, while ensuring their orientations and interaction yields are optimised to efficiently transfer energy to the reaction centres, simultaneously avoiding energy losses due to concentration quenching. The minor group of pigments, the xanthophylls, play a central role in the regulation of light harvesting, defining the antenna efficiency and thus its abilities to simultaneously provide energy to photosystem II and protect itself from excess light damage. Xanthophyll hydrophobicity was found to be a key factor controlling chlorophyll efficiency by modulating pigment–pigment and pigment–protein interactions. Xanthophylls also endow the light harvesting antenna with the remarkable ability to memorise photosystem II light exposure—a light counter principle. Indeed, this type of light harvesting regulation displays hysteretic behaviour, typically observed during electromagnetic induction of ferromagnetic materials, the polarization of ferroelectric materials and the deformation of semi-elastic materials. The photosynthetic antenna is thus a magnificent example of how nature utilises the principles of physics to achieve its goal—extremely efficient, robust, autonomic and yet flexible light harvesting.

Energy and Environmental Science

21531040

10.1016/0042-6989(86)90097-0

On the gekko pupil and scheiner's disc

The four pinhole apertures of the constricted gekko pupil are an adaptation for decreasing the depth of field of the eye, while decreasing the total light flux to the retina. This may be useful for distance estimation at high light levels.

Vision Research

1596497

10.1098/RSBL.2010.0716

Colourful parrot feathers resist bacterial degradation

The brilliant red, orange and yellow colours of parrot feathers are the product of psittacofulvins, which are synthetic pigments known only from parrots. Recent evidence suggests that some pigments in bird feathers function not just as colour generators, but also preserve plumage integrity by increasing the resistance of feather keratin to bacterial degradation. We exposed a variety of colourful parrot feathers to feather-degrading Bacillus licheniformis and found that feathers with red psittacofulvins degraded at about the same rate as those with melanin and more slowly than white feathers, which lack pigments. Blue feathers, in which colour is based on the microstructural arrangement of keratin, air and melanin granules, and green feathers, which combine structural blue with yellow psittacofulvins, degraded at a rate similar to that of red and black feathers. These differences in resistance to bacterial degradation of differently coloured feathers suggest that colour patterns within the Psittaciformes may have evolved to resist bacterial degradation, in addition to their role in communication and camouflage.

Biology Letters

33210396

10.1098/RSBL.2010.0916

Fish mucous cocoons: the ‘mosquito nets’ of the sea

Mucus performs numerous protective functions in vertebrates, and in fishes may defend them against harmful organisms, although often the evidence is contradictory. The function of the mucous cocoons that many parrotfishes and wrasses sleep in, while long used as a classical example of antipredator behaviour, remains unresolved. Ectoparasitic gnathiid isopods (Gnathiidae), which feed on the blood of fish, are removed by cleaner fish during the day; however, it is unclear how parrotfish and wrasse avoid gnathiid attacks at night. To test the novel hypothesis that mucous cocoons protect against gnathiids, we exposed the coral reef parrotfish Chlorurus sordidus (Scaridae) with and without cocoons to gnathiids overnight and measured the energetic content of cocoons. Fish without mucous cocoons were attacked more by gnathiids than fish with cocoons. The energetic content of mucous cocoons was estimated as 2.5 per cent of the fish's daily energy budget fish. Therefore, mucous cocoons protected against attacks by gnathiids, acting like mosquito nets in humans, a function of cocoons and an efficient physiological adaptation for preventing parasite infestation that is not used by any other animal.

Biology Letters

17671336

10.1007/S00572-013-0529-4

Arbuscular mycorrhizal symbiosis modulates antioxidant response in salt-stressed Trigonella foenum-graecum plants

An experiment was conducted to evaluate the influence of Glomus intraradices colonization on the activity of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), peroxidase (PX), ascorbate peroxidase (APX), and glutathione reductase (GR)] and the accumulation of nonenzymatic antioxidants (ascorbic acid, α-tocopherol, glutathione, and carotenoids) in roots and leaves of fenugreek plants subjected to varying degrees of salinity (0, 50, 100, and 200 mM NaCl) at two time intervals (1 and 14 days after saline treatment, DAT). The antioxidative capacity was correlated with oxidative damage in the same tissue. Under salt stress, lipid peroxidation and H2O2 concentration increased with increasing severity and duration of salt stress (DoS). However, the extent of oxidative damage in mycorrhizal plants was less compared to nonmycorrhizal plants. The study reveals that mycorrhiza-mediated attenuation of oxidative stress in fenugreek plants is due to enhanced activity of antioxidant enzymes and higher concentrations of antioxidant molecules. However, the significant effect of G. intraradices colonization on individual antioxidant molecules and enzymes varied with plant tissue, salinity level, and DoS. The significant effect of G. intraradices colonization on antioxidative enzymes was more evident at 1DAT in both leaves and roots, while the concentrations of antioxidant molecules were significantly influenced at 14DAT. It is proposed that AM symbiosis can improve antioxidative defense systems of plants through higher SOD activity in M plants, facilitating rapid dismutation of O2- to H2O2, and subsequent prevention of H2O2 build-up by higher activities of CAT, APX, and PX. The potential of G. intraradices to ameliorate oxidative stress generated in fenugreek plants by salinity was more evident at higher intensities of salt stress.

Mycorrhiza

84914573

10.1080/00063657309476382

Food and Feeding Ecology of Puffins

This study shows that although annual fluctuations occur in the main prey types of Skomer Puffins, food availability does not appear to limit breeding success. Most birds found food close to the colony, showing peaks of activity early in the day and again in late afternoon; and two out of four experimental pairs were able to rear 'twins', though the growth-rates of these were less than for single chicks. Some interesting observations are given on the feeding of the chick and on kleptoparasitism of adults by Jackdaws and gulls.

Bird Study

34359603

10.1242/JEB.063040

The hydrodynamic function of shark skin and two biomimetic applications

SUMMARY It has long been suspected that the denticles on shark skin reduce hydrodynamic drag during locomotion, and a number of man-made materials have been produced that purport to use shark-skin-like surface roughness to reduce drag during swimming. But no studies to date have tested these claims of drag reduction under dynamic and controlled conditions in which the swimming speed and hydrodynamics of shark skin and skin-like materials can be quantitatively compared with those of controls lacking surface ornamentation or with surfaces in different orientations. We use a flapping foil robotic device that allows accurate determination of the self-propelled swimming (SPS) speed of both rigid and flexible membrane-like foils made of shark skin and two biomimetic models of shark skin to measure locomotor performance. We studied the SPS speed of real shark skin, a silicone riblet material with evenly spaced ridges and a Speedo® ‘shark skin-like’ swimsuit fabric attached to rigid flat-plate foils and when made into flexible membrane-like foils. We found no consistent increase in swimming speed with Speedo® fabric, a 7.2% increase with riblet material, whereas shark skin membranes (but not rigid shark skin plates) showed a mean 12.3% increase in swimming speed compared with the same skin foils after removing the denticles. Deformation of the shark skin membrane is thus crucial to the drag-reducing effect of surface denticles. Digital particle image velocimetry (DPIV) of the flow field surrounding moving shark skin foils shows that skin denticles promote enhanced leading-edge suction, which might have contributed to the observed increase in swimming speed. Shark skin denticles might thus enhance thrust, as well as reduce drag.

The Journal of Experimental Biology

85129695

10.1007/S11274-007-9345-3

Microbial degradation of petroleum hydrocarbons in a polluted tropical stream

SummaryCrude oil degradation was observed in water samples from three sites along the course of a polluted stream in Lagos, Nigeria. Consistent increase and decrease in the total viable counts (TVCs) of indigenous organisms occurred in the test and control experiments, respectively. Enrichments of the water samples with crude oil resulted in the isolation of nine bacteria belonging to seven genera. A mixed culture was developed from the assemblage of the nine species. The defined microbial consortium utilized a wide range of pure HCs including cycloalkane and aromatic HCs. Utilization of crude oil and petroleum cuts, i.e., kerosene and diesel resulted in an increase in TVC (till day 10) concomitant with decreases in pH and residual oil concentration. Crude oil, diesel and kerosene were degraded by 88, 85 and 78%, respectively, in 14 days. Substrate uptake studies with axenic cultures showed that growth was not sustainable on either cyclohexane or aromatics while degradation of the petroleum fractions fell below 67% in spite of extended incubation period (20 day). From the GC analysis of recovered oil, while reductions in peaks of n-alkane fractions and in biomarkers namely n-C17/pristane and n-C18/phytane ratios were observed in culture fluids of pure strains, complete removal of all the HC components of kerosene, diesel and crude oil including the isoprenoids was obtained with the consortium within 14 days.

World Journal of Microbiology & Biotechnology

7126723

10.1098/RSIF.2009.0184

Hygromorphs: from pine cones to biomimetic bilayers

We consider natural and artificial hygromorphs, objects that respond to environmental humidity by changing their shape. Using the pine cone as an example that opens when dried and closes when wet, we quantify the geometry, mechanics and dynamics of closure and opening at the cell, tissue and organ levels, building on our prior structural knowledge. A simple scaling theory allows us to quantify the hysteretic dynamics of opening and closing. We also show how simple bilayer hygromorphs of paper and polymer show similar behaviour that can be quantified via a theory which couples fluid transport in a porous medium and evaporative flux to mechanics and geometry. Our work unifies varied observations of natural hygromorphs and suggests interesting biomimetic analogues, which we illustrate using an artificial flower with a controllable blooming and closing response.

Journal of the Royal Society Interface

52827955

10.1371/JOURNAL.PBIO.0040264

The Cyanophage Molecular Mixing Bowl of Photosynthesis Genes

Among the wealth of microbial organisms inhabiting marine environments, cyanobacteria (blue-green algae) are the most abundant photosynthetic cells. Prochlorococcus and Synechococcus, the two most common cyanobacteria, account for 30% of global carbon fixation (through the photosynthetic process in which sugars are manufactured from carbon dioxide and water). By drawing on natural resources, these microbes use photosystems (PS) I and II (the two reaction centers in photosynthesis) to harness energy. Intriguingly, some viruses that infect cyanobacteria (called cyanophage), carry genes that encode two PSII core reaction-center proteins: PsbA (the most rapidly turned over core protein in all oxygen-yielding photosynthetic organisms) and PsbD (which forms a complex with PsbA). By expressing their own copies of psbA and psbD during infection, these cyanophages have managed to co-opt host genes to suit their own purposes: enhancing photosynthesis. It seems likely that they do this in the interests of their own fitness, since cyanophage production is optimal when photosynthesis is maintained during infection. Until recently, only a small sample of cyanophages had been examined, leaving open the questions of how widespread PSII genes are in these organisms and where the genes came from. To answer these questions, Matthew Sullivan, Debbie Lindell, Sallie Chisholm, and colleagues examined a pool of 33 cyanophage isolates (cultured from samples collected from the Sargasso Sea and the Red Sea), along with data already available for nine other cyanophages, for the presence of psbA and psbD genes. They found psbA was present in 88% and psbD in 50% of the cyanophages studied. By analyzing the sequences of these genes along with those from Prochlorococcus and Synechococcus host genes, they reconstructed the evolutionary history of how the PSII genes entered the phage genomes. Cyanophages are divided morphologically into three main families (Podoviridae, Myoviridae, and Siphoviridae). Looking at the distributions of the PSII genes across the different families, Sullivan, Lindell, et al. saw that psbA was present in all myoviruses and all Prochlorococcus podoviruses, but not in Prochlorococcus siphoviruses or Synechococcus podoviruses. The high levels of sequence conservation between the different cyanophages suggest that this gene is probably functional and that it is likely to increase the reproductive fitness of the phage. The length of the latent period may impact the distribution pattern of psbA among these phage groups. However, more information about the physiological characteristics of cyanophages is needed to further investigate these possibilities. The second gene, psbD, was less prolific but was seen in four of the 20 Prochlorococcus myoviruses and 17 of the 20 Synechococcus myoviruses examined—all of which also encoded psbA. Myoviruses are known to infect a wider range of cyanobacteria than the other cyanophage families. Indeed, when investigated, the psbD-encoding myoviruses correlated with those known to have a broader host range. Perhaps the co-opting of both PSII genes ensures a functional PsbA–PsbD protein complex to enhance infection for these cyanophages that are able to infect a wider range of hosts. To determine when the PSII genes had been transferred into the phage and from where, Sullivan, Lindell, et al. investigated the nucleotide sequences of psbA and psbD from both Prochlorococcus and Synechococcus host and cyanophage. Using meticulous sequence analyses and standard statistical methods, they generated phylogenetic trees to explain the evolutionary history of these two PSII genes. By analyzing the clusters of sequence types within the resulting tree, the authors saw evidence that psbA was transferred from the cyanobacteria host genome into the phage genome on four independent occasions and two separate occasions for psbD. Exchange events were generally host-range specific, meaning that Prochlorococcus genes transferred to Prochlorococcus phages, and so on. However, a few intriguing exceptions, where genes did not cluster with their hosts, were observed; these might result from genetic exchange between members of two different phage families (one of broader host range) during co-infection of the same host. Sullivan, Lindell, et al. were also able to use their dataset to investigate a previous suggestion that alterations in the nucleotide distributions within individual PSII genes (creating a kind of patchwork gene) demonstrate that intragenic recombination has taken place. Indeed, they confirm that this occurs among Synechococcus myoviruses and Prochlorococcus podoviruses. In some cases involving Synechococcus, intragenic recombination appears to have happened in both host-to-phage and phage-to-host directions for both genes; and, for some Prochlorococcus genes, DNA from an unknown source also seems to have been inserted. Occasionally, intragenic exchanges are also seen between Synechococcus hosts. The authors compare their cultured results to those from wild phage sequences from the Pacific Ocean and see that much of the natural diversity is similar to the sequences from the cyanophage isolates, despite their origination from different ocean basins. Overall, therefore, a considerable amount of genetic shuffling takes place within these two PSII genes in cyanophages, and this creates a reservoir of photosynthetic diversity from which both host and phage are likely to benefit. This study offers a compelling example of global-scale microbial and phage co-evolution that likely influences the biological success of these prolific marine organisms.

PLOS Biology

28605001

10.1016/J.SCITOTENV.2007.02.009

Revisiting the organohalogens associated with 1979-samples of Brazilian bees (Eufriesea purpurata).

Brazilian bees of the species Eufriesea purpurata are known to tolerate very high concentrations of DDT. As reported in the literature, these bees have suffered no harm from as much as 2 mg/bee, which is in the per-cent range of the body weight. In 1979, individuals of E. purpurata were captured as they collected DDT from walls of remote, rural houses in Brazil. Reported herein are quantities and identities of DDT, DDT metabolites, and other organohalogen compounds in four samples of bees stored since 1979. The concentrations of DDT (sum of p,p'-DDT, -DDE, and -DDD) ranged from 23 to 314 microg/bee which is up to twelve fold higher than the LD(50) value of DDT in the honey bee (Apis mellifera) but significantly lower than the no-effect concentration in E. purpurata. Enantioselective determination confirmed the presence of racemic o,p'-DDT in the four individual samples. GC/ECNI-MS investigation resulted in the detection of low amounts (<1 microg/bee) of PCA, lindane, and chlordane. At higher retention times four unknown compounds were detected with a proposed molecular ion at m/z 498, a non-aromatic hydrocarbon backbone along with the presence of eight chlorine substituents. Neither the structure nor the origin of these compounds could be determined. Considering where and when the bees were collected and considering the biology and ecology of the euglossine bees themselves, we propose that the four unknowns are natural products and, as such, are the most highly chlorinated natural compounds yet discovered.

Science of The Total Environment

4416276

10.1038/439153A

Teaching in tandem-running ants

The ant Temnothorax albipennis uses a technique known as tandem running to lead another ant from the nest to food —with signals between the two ants controlling both the speed and course of the run. Here we analyse the results of this communication and show that tandem running is an example of teaching, to our knowledge the first in a non-human animal, that involves bidirectional feedback between teacher and pupil. This behaviour indicates that it could be the value of information, rather than the constraint of brain size, that has influenced the evolution of teaching.

Nature

38952655

10.1672/0277-5212(2006)26[322:HTSSMV]2.0.CO;2

How tussocks structure sedge meadow vegetation

Carex stricta dominates sedge meadows in southern Wisconsin, USA. In contrast with invasive species that dominate as monotypes, C. stricta supports a diversity of co-occurring species by forming tussocks. Concerns about diversity loss and the potential to restore species-rich tussocks led us to ask how tussocks foster high species richness and affect composition. Our study of 181 tussocks at three sites showed that tussocks structure sedge meadow vegetation by adding both surface area and micro-habitats. Tussocks, which average 15–25 cm tall, increase surface area of an otherwise flat plot by 40%. Species richness was positively correlated with tussock size, but the patterns differed among sites. At a site where water was deep, tussock height was the best predictor of richness; at two other sites, surface area and circumference were the best predictors. Micro-habitats differed in conditions and species composition: tussock tops were high in light, variable in temperature, and high in litter cover. Tussock sides had less litter but more moss; off-tussock areas tended to be aquatic. Of the 56 taxa found, 34 showed significant affinities for one or more micro-habitats. Of these, four species occurred primarily on tops, several extended from tops to lower levels, seven aquatic taxa preferred areas off-tussocks, and one species specialized in tussock sides. Over the 2004 growing season, species richness increased in an additive process, from 35 species in May to 56 in September 2004. Cover of litter and moss increased and bare surface decreased with season, but only seven of the 34 taxa with micro-site preferences expanded their distributions as the September drawdown exposed the off-tussock micro-habitat. We conclude that tussocks enhance species richness in three ways, by increasing surface area, by providing multiple micro-habitats, and by undergoing seasonal changes in composition. Our detailed data on plant-diversity support by large tussocks form a benchmark for tussock meadow conservation, as well as a target for restoration of degraded meadows.

Wetlands

7577489

10.1093/PCP/PCM055

Xyloglucan endo-transglycosylase (XET) functions in gelatinous layers of tension wood fibers in poplar--a glimpse into the mechanism of the balancing act of trees.

Tension wood is a specialized tissue of deciduous trees that functions in bending woody stems to optimize their position in space. Tension wood fibers that develop on one side of the stem have an increased potency to shrink compared with fibers on the opposite side, thus creating a bending moment. It is believed that the gelatinous (G) cell wall layer containing almost pure cellulose of tension wood fibers is pivotal to their shrinking. By analyzing saccharide composition and linkage in isolated G-layers of poplar, we found that they contain some matrix components in addition to cellulose, of which xyloglucan is the most abundant. Xyloglucan, xyloglucan endo-transglycosylase (XET) activity and xyloglucan endo-transglycosylase/hydrolase (XTH) gene products were detected in developing G-layers by labeling using CCRC-M1 monoclonal antibody, in situ incorporation of XXXG-SR and the polyclonal antibody to poplar PttXET16-34, respectively, indicating that xyloglucan is incorporated into the G-layer during its development. Moreover, several XTH transcripts were altered and were generally up-regulated in developing tension wood compared with normal wood. In mature G-fibers, XTH gene products were detected in the G-layers while the XET activity was evident in the adjacent S(2) wall layer. We propose that XET activity is essential for G-fiber shrinking by repairing xyloglucan cross-links between G- and S(2)-layers and thus maintaining their contact. Surprisingly, XTH gene products and XET activity persisted in mature G-fibers for several years, suggesting that the enzyme functions after cell death repairing the cross-links as they are being broken during the shrinking process.

Plant and Cell Physiology

4404922

10.1038/429363A

Pigment chemistry: The red sweat of the hippopotamus

Within a few minutes of perspiration, the colourless, viscous sweat of the hippopotamus gradually turns red, and then brown as the pigment polymerizes. Here we isolate and characterize the pigments responsible for this colour reaction. The unstable red and orange pigments turn out to be non-benzenoid aromatic compounds that are unexpectedly acidic and have antibiotic as well as sunscreen activity.

Nature