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Ai2 1.7k

15291344

10.1242/JEB.00209

The Kármán gait: novel body kinematics of rainbow trout swimming in a vortex street

SUMMARY Most fishes commonly experience unsteady flows and hydrodynamic perturbations during their lifetime. In this study, we provide evidence that rainbow trout Oncorhynchus mykiss voluntarily alter their body kinematics when interacting with vortices present in the environment that are not self-generated. To demonstrate this, we measured axial swimming kinematics in response to changes in known hydrodynamic wake characteristics. We compared trout swimming in the Kármán street behind different diameter cylinders (2.5 and 5 cm) at two flow speeds (2.5 and 4.5 L s-1, where L is total body length) to trout swimming in the free stream and in the cylinder bow wake. Trout swimming behind cylinders adopt a distinctive, previously undescribed pattern of movement in order to hold station, which we term the Kármán gait. During this gait, body amplitudes and curvatures are much larger than those of trout swimming at an equivalent flow velocity in the absence of a cylinder. Tail-beat frequency is not only lower than might be expected for a trout swimming in the reduced flow behind a cylinder, but also matches the vortex shedding frequency of the cylinder. Therefore, in addition to choosing to be in the slower flow velocity offered behind a cylinder (drafting), trout are also altering their body kinematics to synchronize with the shed vortices (tuning), using a mechanism that may not involve propulsive locomotion. This behavior is most distinctive when cylinder diameter is large relative to fish length. While tuning, trout have a longer body wavelength than the prescribed wake wavelength, indicating that only certain regions of the body may need to be oriented in a consistent manner to the oncoming vortices. Our results suggest that fish can capture energy from vortices generated by the environment to maintain station in downstream flow. Interestingly, trout swimming in front of a cylinder display lower tail-beat amplitudes and body wave speeds than trout subjected to any of the other treatments, implying that the bow wake may be the most energetically favorable region for a fish to hold station near a cylinder.

The Journal of Experimental Biology

35809681

10.3852/MYCOLOGIA.97.4.866

The captured launch of a ballistospore.

Ballistospore discharge is a feature of 30000 species of mushrooms, basidiomycete yeasts and pathogenic rusts and smuts. The biomechanics of discharge may involve an abrupt change in the center of mass associated with the coalescence of Buller's drop and the spore. However this process occurs so rapidly that the launch of the ballistospore has never been visualized. Here we report ultra high-speed video recordings of the earliest events of spore dispersal using the yeast Itersonilia perplexans and the distantly related jelly fungus Auricularia auricula. Images taken at camera speeds of up to 100,000 frames/ s demonstrate that ballistospore discharge does involve the coalescence of Buller's drop and the spore. Recordings of I. perplexans demonstrate that although coalescence may result from the directed collapse of Buller's drop onto the spore, it also may involve the movement of the spore toward the drop. The release of surface tension at coalescence provides the energy and directional momentum to propel the drop and spore away from the fungus. Analyses show that ballistospores launch into the air at initial accelerations in excess of 10,000 g. There is no known analog of this micromechanical process in animals, plants or bacteria, but the recent development of a surface tension motor may mimic the fungal biology described here.

Mycologia

86897109

10.2307/2388599

Distribution of Leaf Shapes of Piper sp. in a Tropical Cloud Forest: Evidence for the Role of Drip-tips

Biotropica

7188463

10.1016/J.JBIOMECH.2009.09.053

Dynamic mechanical properties of the tissue-engineered matrix associated with individual chondrocytes.

The success of cell-based tissue engineering approaches in restoring biological function will be facilitated by a comprehensive fundamental knowledge of the temporal evolution of the structure and properties of the newly synthesized matrix. Here, we quantify the dynamic oscillatory mechanical behavior of the engineered matrix associated with individual chondrocytes cultured in vitro for up to 28 days in alginate scaffolds. The magnitude of the complex modulus (|E*|) and phase shift (delta) were measured in culture medium using Atomic Force Microscopy (AFM)-based nanoindentation in response to an imposed oscillatory deformation (amplitude approximately 5nm) as a function of frequency (f=1-316Hz), probe tip geometry (2.5microm radius sphere and 50nm radius square pyramid), and in the absence and presence of growth factors (GF, insulin growth factor-1, IGF-1, and osteogenic protein-1, OP-1). |E*| for all conditions increased nonlinearly with frequency dependence approximately f(1/2) and ranged between approximately 1 and 25kPa. This result, along with theoretical calculations of the characteristic poroelastic relaxation frequency, f(p), (approximately 50-90Hz) suggested that this time-dependent behavior was governed primarily by fluid flow-dependent poroelasticity, rather than flow-independent viscoelastic processes associated with the solid matrix. |E*(f)| increased, (f) decreased, and the hydraulic permeability, k, decreased with time in culture and with growth factor treatment. This trend of a more elastic-like response was thought to be associated with increased macromolecular biosynthesis, density, and a more mature matrix structure/organization.

Journal of Biomechanics

7476773

10.1007/BF01047102

Hydromechanics and biology

SummaryTo exemplify relations between biology and hydrodynamics the Reynolds number range and the effects of viscosity and inertia in swimming and flying organisms is discussed. Comparing water beetles and penguins it is shown, that the technical drag coefficient is an adequate means to describe flow adaptation in animals. Compared to technical systems, especially the penguins' drag coefficient is astonishingly low. Furthermore, the question, why comparatively thick bodies in penguins and dolphins show rather low drag is discussed. Distributed boundary layer damping in dolphins and secretion of special high molecular slimes in fishes help to keep flow characteristics laminar. As an example of one easily understood thrust mechanism, the drag inducing pair of rowing legs in water beetles is morphologically and hydrodynamically analysed. Fish swimming is discussed as a locomotion principle using lift components. Thrust generation by the moving tail fin of a fish is analysed in detail. Coming back to the influence if Reynolds number, it is finally shown, how very small, bristle bearing swimming legs and wings of insects make use of viscosity effects for locomotion.

Biophysics of Structure and Mechanism

135945990

10.1016/0928-4931(94)90039-6

Biomimicking of animal quills and plant stems: natural cylindrical shells with foam cores

Abstract Thin walled cylindrical shell structures are widespread in nature: examples include porcupine quills, hedgehog spines and plant stems. All have an outer shell of almost fully dense material supported by a low density, cellular core. In nature, all are loaded in some combination of axial compression and bending: failure is typically by buckling. Natural structures are often optimized. Here we have investigated and characterized the morphology of several natural tubular structures. Mechanical models recently developed to analyze the elastic buckling of a thin cylindrical shell supported by a soft elastic core (G.N. Karam and L.J. Gibson, Elastic buckling of cylindrical shells with elastic cores, I: Analysis, submitted to Int. J. Solids Structures, 1994 , G.N. Karam and L.J. Gibson, Elastic buckling of cylindrical shells with elastic cores, II: Experiments, submitted to Int. J. Solids Structures, 1994 ) were used to study the mechanical efficiency of these natural structures. It was found that natural structures are often more mechanically efficient than equivalent weight hollow cylinders. Biomimicking of natural cylindrical shell structures may offer the potential to increase the mechanical efficiency of engineering structures.

Materials Science and Engineering: C

30646431

10.1126/SCIENCE.1187936

Microbial Biosynthesis of Alkanes

Toward Alkane Synthesis Alkanes are major components of fossil fuels, and synthesis of alkanes remains a challenge in the conversion of renewable raw materials to fuels. Even though diverse organisms synthesize alkanes, synthesis pathways have remained elusive. Now Schirmer et al. (p. 559) describe an alkane biosynthesis pathway in cyanobacteria that converts intermediates of fatty acid metabolism to alkanes and alkenes. Heterologous expression of the biosynthetic genes resulted in production of alkanes in Escherichia coli. This pathway is likely to be a valuable tool in the production of biofuels. Alkane biosynthesis genes were identified in cyanobacteria and engineered into Escherichia coli for recombinant hydrocarbon production. Alkanes, the major constituents of gasoline, diesel, and jet fuel, are naturally produced by diverse species; however, the genetics and biochemistry behind this biology have remained elusive. Here we describe the discovery of an alkane biosynthesis pathway from cyanobacteria. The pathway consists of an acyl–acyl carrier protein reductase and an aldehyde decarbonylase, which together convert intermediates of fatty acid metabolism to alkanes and alkenes. The aldehyde decarbonylase is related to the broadly functional nonheme diiron enzymes. Heterologous expression of the alkane operon in Escherichia coli leads to the production and secretion of C13 to C17 mixtures of alkanes and alkenes. These genes and enzymes can now be leveraged for the simple and direct conversion of renewable raw materials to fungible hydrocarbon fuels.

Science

4662400

10.1111/J.1095-8312.1993.TB00896.X

Lung ventilation in salamanders and the evolution of vertebrate air-breathing mechanisms

Abstract Functional analysis of lung ventilation in salamanders combined with historical analysis of respiratory pumps provides new perspectives on the evolution of breathing mechanisms in vertebrates. Lung ventilation in the aquatic salamander Necturus maculosus was examined by means of cineradiography, measurement of buccal and pleuroperitoneal cavity pressures, and electromyography of hypaxial musculature. In deoxygenated water Necturus periodically rises to the surface, opens its mouth, expands its buccal cavity to draw in fresh air, exhales air from the lungs, closes its mouth, and then compresses its buccal cavity and pumps air into the lungs. Thus Necturus produces only two buccal movements per breath: one expansion and one compression. Necturus shares the use of this two-stroke buccal pump with lungfishes, frogs and other salamanders. The ubiquitous use of this system by basal sarcopterygians is evidence that a two-stroke buccal pump is the primitive lung ventilation mechanism for sarcopterygian vertebrates. In contrast, basal actinopterygian fishes use a four-stroke buccal pump. In these fishes the buccal cavity expands to fill with expired air, compresses to expel the pulmonary air, expands to fill with fresh air, and then compresses for a second time to pump air into the lungs. Whether the sarcopterygian two-stroke buccal pump and the actinopterygian four-stroke buccal pump arose independently, whether both are derived from a single, primitive osteichthyian breathing mechanism, or whether one might be the primitive pattern and the other derived, cannot be determined Although Necturus and lungfishes both use a two-stroke buccal pump, they differ in their expiration mechanics. Unlike a lungfish (Protopterus), Necturus exhales by contracting a portion of its hypaxial trunk musculature (the m. transversus abdominis) to increase pleuroperitoneal pressure. The occurrence of this same expiratory mechanism in amniotes is evidence that the use of hypaxial musculature for expiration, but not for inspiration, is a primitive tetrapod feature. From this observation we hypothesize that aspiration breathing may have evolved in two stages: initially, from pure buccal pumping to the use of trunk musculature for exhalation but not for inspiration (as in Necturus); and secondarily, to the use of trunk musculature for both exhalation and inhalation by costal aspiration (as in amniotes).

Biological Journal of The Linnean Society

30226462

10.1371/JOURNAL.PONE.0175029

Bamboo-inspired optimal design for functionally graded hollow cylinders

The optimal distribution of the reinforcing fibers for stiffening hollow cylindrical composites is explored using the linear elasticity theory. The spatial distribution of the vascular bundles in wild bamboo, a nature-designed functionally graded material, is the basis for the design. Our results suggest that wild bamboos maximize their flexural rigidity by optimally regulating the radial gradation of their vascular bundle distribution. This fact provides us with a plant-mimetic design principle that enables the realization of high-stiffness and lightweight cylindrical composites.

PLOS ONE

88979968

10.1016/B978-0-12-424301-9.50010-3

4 – ANATOMICAL MECHANISMS OF SEED DISPERSAL

Seed Biology#R##N#Importance, Development, and Germination

17218939

10.1126/SCIENCE.1192534

Efficient Atmospheric Cleansing of Oxidized Organic Trace Gases by Vegetation

Volatiles Versus Vegetation Plants act as both global sources and sinks of highly reactive volatile organic compounds (VOCs). Models typically treat the uptake and degradation of these compounds as if they are mostly unreactive, like other more commonly studied biogenic gases such as ozone. A study by Karl et al. (p. 816, published online 21 October) suggests that VOCs may be more reactive than expected. By monitoring six field sites representing a range of deciduous ecosystems, several oxidized VOCs were found to have high deposition fluxes. Fumigation experiments in the laboratory confirmed that leaves are capable of oxidizing these compounds, and do so through an enzymatic detoxification or stress-response mechanism. Budgets for VOC flux in the atmosphere suggests that, on a global scale, plants may take up significant levels of VOCs in polluted regions, especially in the tropics. Deciduous trees enzymatically remove oxygenated volatile organic compounds from the atmosphere. The biosphere is the major source and sink of nonmethane volatile organic compounds (VOCs) in the atmosphere. Gas-phase chemical reactions initiate the removal of these compounds from the atmosphere, which ultimately proceeds via deposition at the surface or direct oxidation to carbon monoxide or carbon dioxide. We performed ecosystem-scale flux measurements that show that the removal of oxygenated VOC via dry deposition is substantially larger than is currently assumed for deciduous ecosystems. Laboratory experiments indicate efficient enzymatic conversion and potential up-regulation of various stress-related genes, leading to enhanced uptake rates as a response to ozone and methyl vinyl ketone exposure or mechanical wounding. A revised scheme for the uptake of oxygenated VOCs, incorporated into a global chemistry-transport model, predicts appreciable regional changes in annual dry deposition fluxes.

Science

260074

10.1093/JB/MVJ190

Active-site properties of Phrixotrix railroad worm green and red bioluminescence-eliciting luciferases.

The luciferases of the railroad worm Phrixotrix (Coleoptera: Phengodidae) are the only beetle luciferases that naturally produce true red bioluminescence. Previously, we cloned the green- (PxGR) and red-emitting (PxRE) luciferases of railroad worms Phrixotrix viviani and P. hirtus[OLE1]. These luciferases were expressed and purified, and their active-site properties were determined. The red-emitting PxRE luciferase displays flash-like kinetics, whereas PxGR luciferase displays slow-type kinetics. The substrate affinities and catalytic efficiency of PxRE luciferase are also higher than those of PxGR luciferase. Fluorescence studies with 8-anilino-1-naphthalene sulfonic acid and 6-p-toluidino-2-naphthalene sulfonic acid showed that the PxRE luciferase luciferin-binding site is more polar than that of PxGR luciferase, and it is sensitive to guanidine. Mutagenesis and modelling studies suggest that several invariant residues in the putative luciferin-binding site of PxRE luciferase cannot interact with excited oxyluciferin. These results suggest that one portion of the luciferin-binding site of the red-emitting luciferase is tighter than that of PxGR luciferase, whereas the other portion could be more open and polar.

Journal of Biochemistry

20811999

10.1021/JF200486T

Scorpion toxins modify phytopathogenic fungus physiology. A possible source of new fungicides.

Seven toxins (F1-F7) were purified from Tityus discrepans scorpion venom on a C18 HPLC column. The compounds were fungitoxic on Macrophomina phaseolina. The molecular masses of F1-F7 were (Da) 1061.1, 7328.8, 7288.3, 7268.5, 7104.6, 6924.6, and 6823.3, respectively. It is not known if F1 is a small peptide or some other kind of organic molecule. Compounds F2-F7 were peptides. The most potent was F7, with a minimal inhibition concentration of 0.4 μg/μL and a concentration for 50% inhibition of 0.13 μg/μL. Fungal esterase activity was abolished by F2, F3, and F5 and inhibited by 89, 60, 58, and 54% by F4, F6, F7, and F1, respectively. F1, F2, F5, and F7 induced an increase on hyphae chitin wall and septum thickness. Peptides F3-F6 induced efflux of the fluorescent dye Na-CoroNa Red complex from hyphae. Only F5 and F6 were inhibited by the prokaryote sodium channel blockers amiloride and mibefradil. Gas chromatography-mass spectrometry analysis suggested that F1, F5, F6, and F7 altered sterol biosynthesis either by inhibiting ergosterol biosynthesis or by producing ergosterol analogues. The peptides affect M. phaseolina viability by three mechanisms: decreasing esterase activity, altering Na(+) membrane permeability, and altering wall sterol biosynthesis. It seems that interfering with sterol synthesis is an important mechanism behind the effect of the fungicideal toxins. However, the antifungal effects at short times are indicative of a direct esterase inhibition, which, with the increased membrane leakiness to Na(+), makes the fungus inviable.

Journal of Agricultural and Food Chemistry

676133

10.1021/BM050335E

Characterization of a protein-based adhesive elastomer secreted by the Australian frog Notaden bennetti.

When provoked, Notaden bennetti frogs secrete an exudate which rapidly forms a tacky elastic solid ("frog glue"). This protein-based material acts as a promiscuous pressure-sensitive adhesive that functions even in wet conditions. We conducted macroscopic tests in air to assess the tensile strength of moist glue (up to 78 +/- 8 kPa) and the shear strength of dry glue (1.7 +/- 0.3 MPa). We also performed nanomechanical measurements in water to determine the adhesion (1.9-7.2 nN or greater), resilience (43-56%), and elastic modulus (170-1035 kPa) of solid glue collected in different ways. Dry glue contains little carbohydrate and consists mainly of protein. The protein complement is rich in Gly (15.8 mol %), Pro (8.8 mol %), and Glu/Gln (14.1 mol %); it also contains some 4-hydroxyproline (4.6 mol %) but no 5-hydroxylysine or 3,4-dihydroxyphenylalanine (L-Dopa). Denaturing gel electrophoresis of the glue reveals a characteristic pattern of proteins spanning 13-400 kDa. The largest protein (Nb-1R, apparent molecular mass 350-500 kDa) is also the most abundant, and this protein appears to be the key structural component. The solid glue can be dissolved in dilute acids; raising the ionic strength causes the glue components to self-assemble spontaneously into a solid which resembles the starting material. We describe scattering studies on dissolved and solid glue and provide microscopy images of glue surfaces and sections, revealing a porous interior that is consistent with the high water content (85-90 wt %) of moist glue. In addition to compositional similarities with other biological adhesives and well-known elastomeric proteins, the circular dichroism spectrum of dissolved glue is almost identical to that for soluble elastin and electron and scanning probe microscopy images invite comparison with silk fibroins. Covalent cross-linking does not seem to be necessary for the glue to set.

Biomacromolecules

10612837

10.1152/AJPLEGACY.1972.222.1.114

Heat storage in running antelopes: independence of brain and body temperatures.

TAYLOR, C. RICHARD, AND C. P. LYMAN. Heat storage in running antelopes: independence of brain and body temperatures. Am. J. Physiol. 222(l): 114-117. 1972.-Tremendous amounts of heat are produced when antelopes run at high speed. This study tried I) to determine how much of this heat was stored, and 2) to find out if antelopes possess unusual physiological mechanisms for coping with high body temperatures. Large increases in rectal temperature of Thomson’s gazelles (Gasella thomsonii, wt 15 kg) were measured during running : + 3.9 C after 5 min at 40 km hr-1; +4.6 C after 11 min at 25 km hr-l; and +4.3 C after 20 min at 15 km hr? Heat storage accounted for 80-989;‘, of the calculated heat production during running. Brain temperature rose more slowly than rectal or carotid artery temperature. After a 5 min run at 40 km hr-r the brain was 2.7 C cooler than blood in the carotid artery. Blood supplying the brain appears to be cooled via a countercurrent heat exchange with cool blood draining the nasal mucosa (in the carotid rete). Elands (Taurotragus oryx, wt 200 kg) sweated profusely and their rectal temperature equilibrated after a few minutes of running at a slightly higher level: +0.8 C at 25 km hr-l; +0.8 C at 20 km hr-l; +0.7 C at 15 km hr-l; and 3-0.5 C at 10 km hr?

American Journal of Physiology

44412628

10.1038/NCHEMBIO0906-453

Charging the batteries to heal wounds through PI3K

Endogenous electric fields in wounds have been documented for centuries, but they have received little attention from the scientific community. A new study shows that manipulation of these electric fields affects wound healing in vivo and identifies the phosphoinositide 3-kinase signaling pathway as a key component of cell migration in response to electric cues.

Nature Chemical Biology

94260988

10.1080/00218460902782071

Screening Microalgal Cultures in Search of Microbial Exopolysaccharides with Potential as Adhesives

Nearly 800 cultures from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Collection of Living Microalgae (CCLM) were screened for exopolysaccharide (EPS) production by examining the viscosity of conditioned media supernatants. We first established dose-response relationships for the viscosity of reference polysaccharides dissolved in microalgal growth media. Then, using the 40 most viscous CCLM cultures, we confirmed that the viscosity of culture supernatants correlated well with their total sugar (and thus EPS) content. The conditioned medium with the highest viscosity (6.55 cP, equivalent to 1.16 g/L xanthan gum) was produced by a non-axenic isolate of the cyanobacterium Microcystis aeruginosa f. flos-aquae. Two types of bacteria, designated CSIRO501 (Gram-positive) and CSIRO505 (Gram-negative), were subcultured from it. At 20 dry wt% sugar, an exopolymer preparation from CSIRO505 contained substantially more EPS than its counterparts from CSIRO501 or from axenic Microcystis cultures, and it resembled a well-known bacterial EPS (xanthan gum) in being much more effective at bonding wood than PVC. It bonded wooden lap joints with a dry shear strength of 1.5 MPa, four times the value obtained in equivalent tests of a commercial polyvinyl acetate (PVA) glue.

Journal of Adhesion

1735802

10.1242/JEB.068080

A buckling region in locust hindlegs contains resilin and absorbs energy when jumping or kicking goes wrong

SUMMARY If a hindleg of a locust slips during jumping, or misses its target during kicking, energy generated by the two extensor tibiae muscles is no longer expended in raising the body or striking a target. How, then, is the energy in a jump (4100–4800 μJ) or kick (1700 μJ) dissipated? A specialised buckling region found in the proximal hind-tibia where the bending moment is high, but not present in the other legs, buckled and allowed the distal part of the tibia to extend. In jumps when a hindleg slipped, it bent by a mean of 23±14 deg at a velocity of 13.4±9.5 deg ms–1; in kicks that failed to contact a target it bent by 32±16 deg at a velocity of 32.9±9.5 deg ms–1. It also buckled 8.5±4.0 deg at a rate of 0.063±0.005 deg ms–1 when the tibia was prevented from flexing fully about the femur in preparation for both these movements. By experimentally buckling this region through 40 deg at velocities of 0.001–0.65 deg ms–1, we showed that one hindleg could store about 870 μJ on bending, of which 210 μJ was dissipated back to the leg on release. A band of blue fluorescence was revealed at the buckling region under UV illumination that had the two key signatures of the elastic protein resilin. A group of campaniform sensilla 300 μm proximal to the buckling region responded to imposed buckling movements. The features of the buckling region show that it can act as a shock absorber as proposed previously when jumping and kicking movements go wrong.

The Journal of Experimental Biology

56166193

10.1088/0957-4484/13/5/201

Natural strategies for the molecular engineer

The idea of nature as engineer is an old one, but the realization that this metaphor can be extended (should we say retracted?) to the molecular scale has become common currency only over the past two decades or so. Two reasons for this are perhaps paramount. First, the picture of the cell has been transformed from that of a 'wet chemical' melange—'a vessel, filled with a homogeneous solution, in which all chemical processes take place', as Franz Hofmeister put it in 1901—into an image of a sort of fluid factory, a production plant in which molecular machinery works in near-fantastic orchestration to generate complex products from raw materials. This mechanism is self-assembling, self-repairing and self-replicating. The concept of proteins and nucleic acids as 'molecular machines' is now a mainstream one in cell biology. Second, technological advances have made us accustomed to the idea that engineering can be conducted at scales too small to see with the naked eye, yet employing principles—mechanical, electrical, hydraulic, optical, tribological—familiar from the macroscopic world. Molecular electronics and computing, microelectromechanical devices and nanotechnology, are now mainstream concepts, and are validated by at least some degree of physical realization. In this article I shall briefly review some of nature's principles and practices at the molecular, supramolecular and submicrometre scales, and attempt to illustrate how these can be adapted for developing synthetic chemical and materials systems sharing the kind of superior properties and special functions that natural systems exhibit.

Nanotechnology

29499305

10.1021/BM900681W

Spider web glue: two proteins expressed from opposite strands of the same DNA sequence.

The various silks that make up the web of the orb web spiders have been studied extensively. However, success in prey capture depends as much on the web glue as on the fibers. Spider silk glue, which is considered one of the strongest and most effective biological glues, is an aqueous solution secreted from the orb weaving spider's aggregate glands and coats the spiral prey capturing threads of their webs. Studies identified the major component of the glue as microscopic nodules made of a glycoprotein. This study describes two newly discovered proteins that form the glue-glycoprotein of the golden orb weaving spider Nephila clavipes . Our results demonstrate that both proteins contain unique 110 amino acid repetitive domains that are encoded by opposite strands of the same DNA sequence. Thus, the genome of the spider encodes two distinct yet functionally related genes by using both strands of an identical DNA sequence. Moreover, the closest match for the nonrepetitive region of one of the proteins is chitin binding proteins. The web glue appears to have evolved a substantial level of sophistication matching that of the spider silk fibers.

Biomacromolecules

120941839

10.1063/1.2838357

Elastic response of the resurrection fern Polypodium polypodioides during rehydration

The resurrection fern (Polypodium polypodioides) has a remarkable elastic reponse, where the fast water uptake of the fern upon rehydration is accompanied by a significant reduction in its Young’s modulus. In this letter, we discuss the fern’s elastic response and suggest that by mimicking its structure, one should be able to design materials exhibiting interesting elastic behavior.

Applied Physics Letters

15077000

10.1242/JEB.028282

Spider silk as a novel high performance biomimetic muscle driven by humidity

SUMMARY The abrupt halt of a bumble bee's flight when it impacts the almost invisible threads of an orb web provides an elegant example of the amazing strength and toughness of spider silk. Spiders depend upon these properties for survival, yet the impressive performance of silk is not limited solely to tensile mechanics. Here, we show that silk also exhibits powerful cyclic contractions, allowing it to act as a high performance mimic of biological muscles. These contractions are actuated by changes in humidity alone and repeatedly generate work 50 times greater than the equivalent mass of human muscle. Although we demonstrate that this response is general and occurs weakly in diverse hydrophilic materials, the high modulus of spider silk is such that it generates exceptional force. Furthermore, because this effect already operates at the level of single silk fibers, only 5 μm in diameter, it can easily be scaled across the entire size range at which biological muscles operate. By contrast, the most successful synthetic muscles developed so far are driven by electric voltage, such that they cannot scale easily across large ranges in cross-sectional areas. The potential applicability of silk muscles is further enhanced by our finding that silkworm fibers also exhibit cyclic contraction because they are already available in commercial quantities. The simplicity of using wet or dry air to drive the biomimetic silk muscle fibers and the incredible power generated by silk offer unique possibilities in designing lightweight and compact actuators for robots and micro-machines, new sensors, and green energy production.

The Journal of Experimental Biology

55603031

10.3897/JHR.35.4783

Function of the Dufour’s gland in solitary and social Hymenoptera

The poison gland and Dufour's gland are the two glands associated with the sting apparatus in female Apocrita (Hymenoptera). While the poison gland usually functions as an integral part of the venom delivery system, the Dufour's gland has been found to differ in its function in various hymenopteran groups. Like all exocrine glands, the function of the Dufour's gland is to secrete chemicals, but the nature and function of the secretions varies in different taxa. Functions of the Dufour's gland secretions range from serving as a component of material used in nest building, larval food, and pheromones involved in communicative functions that are important for both solitary and social species. This review summarizes the different functions reported for the Dufour's gland in hymenopterans, illustrating how the Dufour's gland secretions can be adapted to give rise to various functions in response to different challenges posed by the ways of life followed by different taxa. Aspects of development, structure, chemistry and the evolution of different functions are also touched upon briefly.

Journal of Hymenoptera Research

2955378

10.1098/RSPB.2010.2203

Bioluminescent signals spatially amplified by wavelength-specific diffusion through the shell of a marine snail

Some living organisms produce visible light (bioluminescence) for intra- or interspecific visual communication. Here, we describe a remarkable bioluminescent adaptation in the marine snail Hinea brasiliana. This species produces a luminous display in response to mechanical stimulation caused by encounters with other motile organisms. The light is produced from discrete areas on the snail's body beneath the snail's shell, and must thus overcome this structural barrier to be viewed by an external receiver. The diffusion and transmission efficiency of the shell is greater than a commercial diffuser reference material. Most strikingly, the shell, although opaque and pigmented, selectively diffuses the blue-green wavelength of the species bioluminescence. This diffusion generates a luminous display that is enlarged relative to the original light source. This unusual shell thus allows spatially amplified outward transmission of light communication signals from the snail, while allowing the animal to remain safely inside its hard protective shell.

Proceedings of The Royal Society B: Biological Sciences

11771568

10.1016/J.CUB.2014.07.059

Archerfish Actively Control the Hydrodynamics of Their Jets

Among tool-using animals [1-4], none are known to adaptively change the hydrodynamic properties of a free jet of water--a task considered difficult in human technology [5-7]. Hunting archerfish can strike their targets with precisely aimed water jets (e.g., [8, 9]), but they are also presently thought to be unable to actively control the hydrodynamics of their jets [8-13]. By using specifically trained fish, we were able to monitor several aspects of jet production and propagation as the fish fired at targets over a much wider range of distances than previously explored [10, 13]. We show that jets that have to travel farther also live longer. Furthermore, the time needed until water assembles at the jet tip is not fixed. Rather, it is adjusted so that maximum focusing occurs just before impact. Surprisingly, the fish achieve this by modulating the dynamics of changes in the cross-section of their mouth opening, a mechanism that seems to not have been applied yet in human-built nozzles. The timing adjustments archerfish make in order to powerfully hit targets over an extended range strikingly parallel the situation in the "uniquely human" ability of powerful throwing [14-18]. Based on the key role throwing played in human encephalization and cognitive evolution [14-20], skillfully "throwing" water should similarly have led to the correlated rapid evolution of cognitive skills in this animal.

Current Biology

85332902

10.3996/NAFA.74.0001

Ecology and Biology of the Pacific Walrus, Odobenus Rosmarus Divergens Illiger

AbstractThe distribution, physical development, pelage, dentition, feeding behavior, reproduction, causes of mortality, and population structure of the Pacific walrus (Odobenus rosmarus divergens) were studied intermittently from 1952 to 1979. In winter, these animals tend to concentrate in north-central and southeastern Bering Sea, where sea ice conditions are most favorable for them. In summer, they concentrate mainly in northwestern and northeastern Chukchi Sea, along the edge of the ice. Most of the northward migrants are females and young; a large proportion of the adult males remains in the Bering Sea throughout the summer. Pacific walruses show strong sexual dimorphism; adult males are about 18% longer and 45% heavier and tend to have larger, more divergent tusks, as well as thicker, lighter-colored, and less hairy skin than adult females. As in other sexually dimorphic otarioid pinnipeds, males undergo secondary growth, beginning about the time of puberty and ending in full physical maturity about...

North American Fauna

240833

10.1007/S00360-010-0470-1

Quadrupedal locomotor performance in two species of arboreal squirrels: predicting energy savings of gliding

Gliding allows mammals to exploit canopy habitats of old-growth forests possibly as a means to save energy. To assess costs of quadrupedal locomotion for a gliding arboreal mammal, we used open-flow respirometry and a variable-speed treadmill to measure oxygen consumption and to calculate cost of transport, excess exercise oxygen consumption, and excess post-exercise oxygen consumption for nine northern flying squirrels (Glaucomys sabrinus) and four fox squirrels (Sciurus niger). Our results indicate that oxygen consumption during exercise by flying squirrels was 1.26–1.65 times higher than predicted based on body mass, and exponentially increased with velocity (from 0.84 ± 0.03 ml O2 kg−1 s−1 at 0.40 m s−1 to 1.55 ± 0.03 ml O2 kg−1 s−1 at 0.67 m s−1). Also, cost of transport in flying squirrels increased with velocity, although excess exercise oxygen consumption and excess post-exercise oxygen consumption did not. In contrast, oxygen consumption during exercise for fox squirrels was similar to predicted, varying from 0.51 (±0.02) ml O2 kg−1 s−1 at 0.63 m s−1 to 0.54 (±0.03) ml O2 kg−1 s−1 at 1.25 m s−1. In addition, the cost of transport for fox squirrels decreased with velocity, while excess exercise oxygen consumption and excess post-exercise oxygen consumption did not. Collectively, these observations suggest that unlike fox squirrels, flying squirrels are poorly adapted to prolonged bouts of quadrupedal locomotion. The evolution of skeletal adaptations to climbing, leaping, and landing and the development of a gliding membrane likely has increased the cost of quadrupedal locomotion by >50% while resulting in energy savings during gliding and reduction in travel time between foraging patches.

Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology

23407670

10.1093/JEE/99.4.1046

Mediation of pyrethroid insecticide toxicity to honey bees (Hymenoptera: Apidae) by cytochrome P450 monooxygenases.

Honey bees, Apis mellifera L., often thought to be extremely susceptible to insecticides in general, exhibit considerable variation in tolerance to pyrethroid insecticides. Although some pyrethroids, such as cyfluthrin and lambda-cyhalothrin, are highly toxic to honey bees, the toxicity of tau-fluvalinate is low enough to warrant its use to control parasitic mites inside honey bee colonies. Metabolic insecticide resistance in other insects is mediated by three major groups of detoxifying enzymes: the cytochrome P450 monooxygenases (P450s), the carboxylesterases (COEs), and the glutathione S-transferases (GSTs). To test the role of metabolic detoxification in mediating the relatively low toxicity of tau-fluvalinate compared with more toxic pyrethroid insecticides, we examined the effects of piperonyl butoxide (PBO), S,S,S-tributylphosphorotrithioate (DEF), and diethyl maleate (DEM) on the toxicity of these pyrethroids. The toxicity of the three pyrethroids to bees was greatly synergized by the P450 inhibitor PBO and synergized at low levels by the carboxylesterase inhibitor DEF. Little synergism was observed with DEM. These results suggest that metabolic detoxification, especially that mediated by P450s, contributes significantly to honey bee tolerance of pyrethroid insecticides. The potent synergism between tau-fluvalinate and PBO suggests that P450s are especially important in the detoxification of this pyrethroid and explains the ability of honey bees to tolerate its presence.

Journal of Economic Entomology

122872949

10.1063/1.2841818

Templated biomimetic multifunctional coatings

We report a bioinspired templating technique for fabricating multifunctional optical coatings that mimic both unique functionalities of antireflective moth eyes and superhydrophobic cicada wings. Subwavelength-structured fluoropolymer nipple arrays are created by a soft-lithography-like process. The utilization of fluoropolymers simultaneously enhances the antireflective performance and the hydrophobicity of the replicated films. The specular reflectivity matches the optical simulation using a thin-film multilayer model. The dependence of the size and the crystalline ordering of the replicated nipples on the resulting antireflective properties have also been investigated by experiment and modeling. These biomimetic materials may find important technological application in self-cleaning antireflection coatings.

Applied Physics Letters

27315962

10.1242/JEB.028944

How super is supercontraction? Persistent versus cyclic responses to humidity in spider dragline silk

SUMMARY Spider dragline silk has enormous potential for the development of biomimetic fibers that combine strength and elasticity in low density polymers. These applications necessitate understanding how silk reacts to different environmental conditions. For instance, spider dragline silk `supercontracts' in high humidity. During supercontraction, unrestrained dragline silk contracts up to 50% of its original length and restrained fibers generate substantial stress. Here we characterize the response of dragline silk to changes in humidity before, during and after supercontraction. Our findings demonstrate that dragline silk exhibits two qualitatively different responses to humidity. First, silk undergoes a previously unknown cyclic relaxation–contraction response to wetting and drying. The direction and magnitude of this cyclic response is identical both before and after supercontraction. By contrast, supercontraction is a `permanent' tensioning of restrained silk in response to high humidity. Here, water induces stress, rather than relaxation and the uptake of water molecules results in a permanent change in molecular composition of the silk, as demonstrated by thermogravimetric analysis (TGA). Even after drying, silk mass increased by∼ 1% after supercontraction. By contrast, the cyclic response to humidity involves a reversible uptake of water. Dried, post-supercontraction silk also differs mechanically from virgin silk. Post-supercontraction silk exhibits reduced stiffness and stress at yield, as well as changes in dynamic energy storage and dissipation. In addition to advancing understanding supercontraction, our findings open up new applications for synthetic silk analogs. For example, dragline silk emerges as a model for a biomimetic muscle, the contraction of which is precisely controlled by humidity alone.

The Journal of Experimental Biology

84368749

10.1016/0022-1910(80)90098-0

Volatile fatty acids and methane production in relation to anaerobic carbohydrate fermentation in Oryctes nasicornis larvae (Coleoptera: Scarabaeidae).

Abstract Physico-chemical investigations into the conditions of cellulose digestion by Oryctes nasicornis larvae show that the intestinal contents constitute a reducing alkaline medium. The mesenteron presents facultative conditions and high pH values whereas in the proctodeum anaerobiosis is strict and the pH approaches neutrality. No cellulase activity is detected either in the gut walls or the contents. Among the products of polysaccharide fermentation, volatile fatty acids (VFA) and methane are identified. The VFAs are 3 or 4 times more concentrated in the mesenteron than in the proctodeal dilation and acetic acid predominates. The VFAs, which are also present in the haemolymph, must cross the intestinal barrier. Methane formation takes place exclusively in the proctodeal dilation from which it is released to the exterior.

Journal of Insect Physiology

32862374

10.1002/RCM.997

Mycosporine-glutamicol-glucoside: a natural UV-absorbing secondary metabolite of rock-inhabiting microcolonial fungi.

Microcolonial ascomycetes are known to inhabit bare rock surfaces in cold and hot deserts and thus are habitually exposed to high levels of solar radiation. Several of these stress-tolerant fungal isolates, cultivated in the laboratory under daylight illumination, were studied for the presence of effective UV-radiation protection substances. Liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) analyses allowed for efficient separation and structure clarification of two mycosporines. It was demonstrated that both mycosporine-glutamicol-glucoside and mycosporine-glutaminol-glucoside are natural and constitutive secondary metabolites of microcolonial fungi. The function and relation of these substances in the fungal cell are discussed.

Rapid Communications in Mass Spectrometry

752457

10.1038/ISMEJ.2007.75

The geomicrobiology of gold

Microorganisms capable of actively solubilizing and precipitating gold appear to play a larger role in the biogeochemical cycling of gold than previously believed. Recent research suggests that bacteria and archaea are involved in every step of the biogeochemical cycle of gold, from the formation of primary mineralization in hydrothermal and deep subsurface systems to its solubilization, dispersion and re-concentration as secondary gold under surface conditions. Enzymatically catalysed precipitation of gold has been observed in thermophilic and hyperthermophilic bacteria and archaea (for example, Thermotoga maritime, Pyrobaculum islandicum), and their activity led to the formation of gold- and silver-bearing sinters in New Zealand's hot spring systems. Sulphate-reducing bacteria (SRB), for example, Desulfovibrio sp., may be involved in the formation of gold-bearing sulphide minerals in deep subsurface environments; over geological timescales this may contribute to the formation of economic deposits. Iron- and sulphur-oxidizing bacteria (for example, Acidothiobacillus ferrooxidans, A. thiooxidans) are known to breakdown gold-hosting sulphide minerals in zones of primary mineralization, and release associated gold in the process. These and other bacteria (for example, actinobacteria) produce thiosulphate, which is known to oxidize gold and form stable, transportable complexes. Other microbial processes, for example, excretion of amino acids and cyanide, may control gold solubilization in auriferous top- and rhizosphere soils. A number of bacteria and archaea are capable of actively catalysing the precipitation of toxic gold(I/III) complexes. Reductive precipitation of these complexes may improve survival rates of bacterial populations that are capable of (1) detoxifying the immediate cell environment by detecting, excreting and reducing gold complexes, possibly using P-type ATPase efflux pumps as well as membrane vesicles (for example, Salmonella enterica, Cupriavidus (Ralstonia) metallidurans, Plectonema boryanum); (2) gaining metabolic energy by utilizing gold-complexing ligands (for example, thiosulphate by A. ferrooxidans) or (3) using gold as metal centre in enzymes (Micrococcus luteus). C. metallidurans containing biofilms were detected on gold grains from two Australian sites, indicating that gold bioaccumulation may lead to gold biomineralization by forming secondary ‘bacterioform’ gold. Formation of secondary octahedral gold crystals from gold(III) chloride solution, was promoted by a cyanobacterium (P. boryanum) via an amorphous gold(I) sulphide intermediate. ‘Bacterioform’ gold and secondary gold crystals are common in quartz pebble conglomerates (QPC), where they are often associated with bituminous organic matter possibly derived from cyanobacteria. This may suggest that cyanobacteria have played a role in the formation of the Witwatersrand QPC, the world's largest gold deposit.

The ISME Journal

17790553

10.1242/JEB.005116

Extreme anoxia tolerance in embryos of the annual killifish Austrofundulus limnaeus: insights from a metabolomics analysis

SUMMARY The annual killifish Austrofundulus limnaeus survives in ephemeral pond habitats by producing drought-tolerant diapausing embryos. These embryos probably experience oxygen deprivation as part of their normal developmental environment. We assessed the anoxia tolerance of A. limnaeus embryos across the duration of embryonic development. Embryos develop a substantial tolerance to anoxia during early development, which peaks during diapause II. This extreme tolerance of anoxia is retained during the first 4 days of post-diapause II development and is then lost. Metabolism during anoxia appears to be supported mainly by production of lactate, with alanine and succinate production contributing to a lesser degree. Anoxic embryos also accumulate large quantities of γ-aminobutyrate (GABA), a potential protector of neural function. It appears that the suite of characters associated with normal development and entry into diapause II in this species prepares the embryos for long-term survival in anoxia even while the embryos are exposed to aerobic conditions. This is the first report of such extreme anoxia tolerance in a vertebrate embryo, and introduces a new model for the study of anoxia tolerance in vertebrates.

The Journal of Experimental Biology

29218220

10.1098/RSPB.2008.1281

Insects had it first: surfactants as a defence against predators

Insects have evolved an astonishing array of defences to ward off enemies. Well known and widespread is the regurgitation of oral secretion (OS), fluid that repels attacking predators. In herbivores, the effectiveness of OS has been ascribed so far to the presence of deterrent secondary metabolites sequestered from the host plant. This notion implies, however, that generalists experience less protection on plants with low amounts of secondary metabolites or with compounds ineffective against potential enemies. Resolving the dilemma, we describe a novel defence mechanism that is independent of deterrents as it relies on the intrinsic detergent properties of the OS. The OS of Spodoptera exigua (and other species) was found to be highly amphiphilic and well capable of wetting the hydrophobic cuticle of predatory ants. As a result, affected ants stopped attacking and engaged in extensive cleansing. The presence of surfactants was sufficient to explain the defensive character of herbivore OS. We hypothesize that detergency is a common but unrecognized mode of defence, which provides a base level of protection that may or may not be further enhanced by plant-derived deterrents. Our study also proves that insects ‘invented’ the use of defensive surfactants long before modern agriculture had started applying them as insecticides.

Proceedings of The Royal Society B: Biological Sciences

4192150

10.1038/262284A0

Fog basking by the Namib Desert beetle, Onymacris unguicularis

THE Namib Desert along the south-western coast of Africa supports a sand dune fauna without counterpart elsewhere in the world1. The trophic base of the arthropod fauna is wind-blown detritus2. Aperiodic advective fog collection from vegetation3 or detritus4 is a possible source of water for diverse Namib animals. For the specialised fauna living in vegetation-less dunes, fog collection from detritus4, disturbed sand projections5, directly from humid air6, or from water precipitated on the body4,7, seem to be the only possible water uptake methods. Water uptake from saturated or subsaturated air, demonstrated for a few arthropod species6, is not a physiological capability of Namib tenebrionids already investigated4,6,7.

Nature

18672514

10.1038/SREP06004

Under- and over-water halves of Gyrinidae beetle eyes harbor different corneal nanocoatings providing adaptation to the water and air environments

Whirligig beetles (Gyrinidae) inhabit water surfaces and possess unique eyes which are split into the overwater and underwater parts. In this study we analyze the micro- and nanostructure of the split eyes of two Gyrinidae beetles genera, Gyrinus and Orectochilus. We find that corneae of the overwater ommatidia are covered with maze-like nanostructures, while the corneal surface of the underwater eyes is smooth. We further show that the overwater nanostructures possess no anti-wetting, but the anti-reflective properties with the spectral preference in the range of 450–600 nm. These findings illustrate the adaptation of the corneal nanocoating of the two halves of an insect's eye to two different environments. The novel natural anti-reflective nanocoating we describe may find future technological applications.

Scientific Reports

14454191

10.1016/J.CUB.2011.08.011

Females floated first in bubble-rafting snails

Summary Ever since Mivart asked Darwin to explain a bird's use for half a wing, biologists have been challenged to explain extraordinary evolutionary change mechanistically. Here, we investigate the enigmatic evolutionary origins of Janthinidae, a family of marine snails that raft passively in the neuston, a vast oceanic surface habitat, by constructing floats of mucus bubbles. We present the first molecular phylogeny including Janthinidae, which confirms that janthinids are derived from Epitoniidae (wentletraps) — benthic predators and parasites of sea anemones and corals. Our data support the hypothesis that floats and rafting evolved via modified epitoniid egg masses rather than by juvenile droguing. Our phylogeny also reveals sequential modifications of float formation and function among janthinid lineages. We interpret these changes as sequential adaptations to a neustonic existence, a conclusion supported by the positive association of derived janthinid traits with ecological prevalence.

Current Biology

3629546

10.1016/J.PHYTOCHEM.2010.06.020

Secondary metabolites of Bagassa guianensis Aubl. wood: a study of the chemotaxonomy of the Moraceae family.

In order to explain the durability of the Moraceae plant family, phytochemistry of Bagassa guianensis was performed. Ethyl acetate extract was obtained from the heartwood and 18 secondary metabolites were isolated, including 6 moracins [6-O-methyl-moracin M, 6-O-methyl-moracin N and moracin Z; previously identified: moracin M, moracin N and moracin P], 8 stilbenoids [presently identified: (-)-epialboctalol and arachidin 4; previously identified: alboctalol, trans-resveratrol, arachidin 2, trans-oxyresveratrol and artogomezianol], 3 previously identified flavonoids, steppogenin, katuranin and dihydromorin, beta-sitosterol and resorcinol. Previous studies suggest that stilbenoids are responsible for the natural durability of wood. Our study has determined that B. guianensis is closely related to Morus sp. in phylogeny and should be included in the Moreae sensu stricto tribe of the Moraceae family.

Phytochemistry

4416090

10.1038/438442A

Insect communication: ‘No entry’ signal in ant foraging

Forager ants lay attractive trail pheromones to guide nestmates to food, but the effectiveness of foraging networks might be improved if pheromones could also be used to repel foragers from unrewarding routes. Here we present empirical evidence for such a negative trail pheromone, deployed by Pharaoh's ants (Monomorium pharaonis) as a ‘no entry’ signal to mark an unrewarding foraging path. This finding constitutes another example of the sophisticated control mechanisms used in self-organized ant colonies.

Nature

11389480

10.1063/1.2960720

Crawling beneath the free surface: Water snail locomotion

Land snails move via adhesive locomotion. Through muscular contraction and expansion of their foot, they transmit waves of shear stress through a thin layer of mucus onto a solid substrate. Since a free surface cannot support shear stress, adhesive locomotion is not a viable propulsion mechanism for water snails that travel inverted beneath the free surface. Nevertheless, the motion of the freshwater snail, Sorbeoconcha physidae, is reminiscent of that of its terrestrial counterparts, being generated by the undulation of the snail foot that is separated from the free surface by a thin layer of mucus. Here, a lubrication model is used to describe the mucus flow in the limit of small-amplitude interfacial deformations. By assuming the shape of the snail foot to be a traveling sine wave and the mucus to be Newtonian, an evolution equation for the interface shape is obtained and the resulting propulsive force on the snail is calculated. This propulsive force is found to be nonzero for moderate values of the c...

Physics of Fluids

31340124

10.1242/JEB.029884

Barnacle cement: a polymerization model based on evolutionary concepts

SUMMARY Enzymes and biochemical mechanisms essential to survival are under extreme selective pressure and are highly conserved through evolutionary time. We applied this evolutionary concept to barnacle cement polymerization, a process critical to barnacle fitness that involves aggregation and cross-linking of proteins. The biochemical mechanisms of cement polymerization remain largely unknown. We hypothesized that this process is biochemically similar to blood clotting, a critical physiological response that is also based on aggregation and cross-linking of proteins. Like key elements of vertebrate and invertebrate blood clotting, barnacle cement polymerization was shown to involve proteolytic activation of enzymes and structural precursors, transglutaminase cross-linking and assembly of fibrous proteins. Proteolytic activation of structural proteins maximizes the potential for bonding interactions with other proteins and with the surface. Transglutaminase cross-linking reinforces cement integrity. Remarkably, epitopes and sequences homologous to bovine trypsin and human transglutaminase were identified in barnacle cement with tandem mass spectrometry and/or western blotting. Akin to blood clotting, the peptides generated during proteolytic activation functioned as signal molecules, linking a molecular level event (protein aggregation) to a behavioral response (barnacle larval settlement). Our results draw attention to a highly conserved protein polymerization mechanism and shed light on a long-standing biochemical puzzle. We suggest that barnacle cement polymerization is a specialized form of wound healing. The polymerization mechanism common between barnacle cement and blood may be a theme for many marine animal glues.

The Journal of Experimental Biology

36585357

10.1111/J.1600-0838.2005.00467.X

Strength at the extracellular matrix–muscle interface

Mechanical force is generated within skeletal muscle cells by contraction of specialized myofibrillar proteins. This paper explores how the contractile force generated at the sarcomeres within an individual muscle fiber is transferred through the connective tissue to move the bones. The initial key point for transfer of the contractile force is the muscle cell membrane (sarcolemma) where force is transferred laterally to the basement membrane (specialized extracellular matrix rich in laminins) to be integrated within the connective tissue (rich in collagens) before transmission to the tendons. Connections between (1) key molecules outside the myofiber in the basement membrane to (2) molecules within the sarcolemma of the myofiber and (3) the internal cytoplasmic structures of the cytoskeleton and sarcomeres are evaluated. Disturbances to many components of this complex interactive system adversely affect skeletal muscle strength and integrity, and can result in severe muscle diseases. The mechanical aspects of these crucial linkages are discussed, with particular reference to defects in laminin‐α2 and integrin‐α7. Novel interventions to potentially increase muscle strength and reduce myofiber damage are mentioned, and these are also highly relevant to muscle diseases and aging muscle.

Scandinavian Journal of Medicine & Science in Sports

9068384

10.1073/PNAS.1006872107

Synergy of multiple partners, including freeloaders, increases host fitness in a multispecies mutualism

Understanding cooperation is a central challenge in biology, because natural selection should favor “free-loaders” that reap benefits without reciprocating. For interspecific cooperation (mutualism), most approaches to this paradox focus on costs and benefits of individual partners and the strategies mutualists use to associate with beneficial partners. However, natural selection acts on lifetime fitness, and most mutualists, particularly longer-lived species interacting with shorter-lived partners (e.g., corals and zooxanthellae, tropical trees and mycorrhizae) interact with multiple partner species throughout ontogeny. Determining how multiple partnerships might interactively affect lifetime fitness is a crucial unexplored link in understanding the evolution and maintenance of cooperation. The tropical tree Acacia drepanolobium associates with four symbiotic ant species whose short-term individual effects range from mutualistic to parasitic. Using a long-term dataset, we show that tree fitness is enhanced by partnering sequentially with sets of different ant symbionts over the ontogeny of a tree. These sets include a “sterilization parasite” that prevents reproduction and another that reduces tree survivorship. Trees associating with partner sets that include these “parasites” enhance lifetime fitness by trading off survivorship and fecundity at different life stages. Our results demonstrate the importance of evaluating mutualism within a community context and suggest that lifespan inequalities among mutualists may help cooperation persist in the face of exploitation.

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

21233010

10.1093/JXB/ERT279

Integrative biomechanics for tree ecology: beyond wood density and strength.

Functional ecology has long considered the support function as important, but its biomechanical complexity is only just being elucidated. We show here that it can be described on the basis of four biomechanical traits, two safety traits against winds and self-buckling, and two motricity traits involved in sustaining an upright position, tropic motion velocity (MV) and posture control (PC). All these traits are integrated at the tree scale, combining tree size and shape together with wood properties. The assumption of trait constancy has been used to derive allometric scaling laws, but it was more recently found that observing their variations among environments and functional groups, or during ontogeny, provides more insights into adaptive syndromes of tree shape and wood properties. However, oversimplified expressions have often been used, possibly concealing key adaptive drivers. An extreme case of oversimplification is the use of wood basic density as a proxy for safety. Actually, as wood density is involved in stiffness, loads, and construction costs, the impact of its variations on safety is non-trivial. Moreover, other wood features, especially the microfibril angle (MFA), are also involved. Furthermore, wood is not only stiff and strong, but it also acts as a motor for MV and PC. The relevant wood trait for this is maturation strain asymmetry. Maturation strains vary with cell-wall characteristics such as MFA, rather than with wood density. Finally, the need for further studies about the ecological relevance of branching patterns, motricity traits, and growth responses to mechanical loads is discussed.

Journal of Experimental Botany

23510429

10.1007/BF00660177

Die Spiegeloptik des Flußkrebsauges

SummaryIn the superposition eye of the crayfish (Astacus leptodactylus), images are formed by radial plane mirrors arranged in an orthogonal pattern. The optical structure of the crayfish eye can be described as a family of virtual reflecting cone envelopes concentric around each direction in space. There exist two reflection mechanisms: total internal reflection at the sides of the crystalline cones and reflection by multilayer mirrors attached to the distal parts of the cones. Image-forming rays have to be reflected twice in the general case, and once in the case of perpendicular position of the plane of incidence and the mirror plane. For rays incident at small angles to the ommatidial axis, this condition is almost satisfied due to a particular axial variation of the refractive index of the crystalline cone, and for rays incident at large angles, due to the spectral reflecting properties of the multilayer reflector.

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

23126550

10.1007/S00442-006-0614-X

The narrow-leaf syndrome: a functional and evolutionary approach to the form of fog-harvesting rosette plants

Plants that use fog as an important water-source frequently have a rosette growth habit. The performance of this morphology in relation to fog interception has not been studied. Some first-principles from physics predict that narrow leaves, together with other ancillary traits (large number and high flexibility of leaves, caudices, and/or epiphytism) which constitute the “narrow-leaf syndrome” should increase fog-interception efficiency. This was tested using aluminum models of rosettes that differed in leaf length, width and number and were exposed to artificial fog. The results were validated using seven species of Tillandsia and four species of xerophytic rosettes. The total amount of fog intercepted in rosette plants increased with total leaf area, while narrow leaves maximized interception efficiency (measured as interception per unit area). The number of leaves in the rosettes is physically constrained because wide-leafed plants can only have a few blades. At the limits of this constraint, net fog interception was independent of leaf form, but interception efficiency was maximized by large numbers of narrow leaves. Atmospheric Tillandsia species show the narrow-leaf syndrome. Their fog interception efficiencies were correlated to the ones predicted from aluminum-model data. In the larger xerophytic rosette species, the interception efficiency was greatest in plants showing the narrow-leaf syndrome. The adaptation to fog-harvesting in several narrow-leaved rosettes was tested for evolutionary convergence in 30 xerophytic rosette species using a comparative method. There was a significant evolutionary tendency towards the development of the narrow-leaf syndrome the closer the species grew to areas where fog is frequently available. This study establishes convergence in a very wide group of plants encompassing genera as contrasting as Tillandsia and Agave as a result of their dependence on fog.

Oecologia

83972926

10.1046/J.1365-3040.1998.00336.X

The mechanism of floral heliotropism in the snow buttercup, Ranunculus adoneus

ABSTRACT We designed field experiments using solar-trackingRanunculus adoneusflowers to determine where photo-reception occurred, which organs responded, and howmovement was achieved. Flower peduncles bend eastwardin the morning and gradually unbend over the course ofthe day. Peduncles were found to bend significantly morefrequently in the middle region near the floral bracts,1–3 cm below the flower, than elsewhere on the peduncle.Because the peduncle tip continued to track the sun evenafter the flower itself was removed, our experiments con-centrated on shielding (or conversely, exposing) variousportions of peduncles from (or to) sunlight. Photo-reception occurred primarily in the portion of the stemjust beneath the floral receptacle. By following the posi-tion of landmarks applied to the stem, we found that 40%more growth occurred on the shaded side of bent pedun-cles, compared to the sunlit side. In contrast, top-shieldedpeduncles did not solar track well and grew only 25%more on the shaded side than on the sunlit side. Thisgrowth differential corresponded to differences in celllength on the two sides of bent peduncles, with signifi-cantly longer epidermal cells occurring on the shaded sidethan on the sunlit side.Key-words: Ranunculus adoneus; snow buttercup; helio-tropism; phototropism; solar tracking.

Plant Cell and Environment

85849989

10.1007/S00227-004-1334-6

Carrion-feeding on the sediment surface at nocturnal low tides by the polychaete Phyllodoce mucosa

Harsh physical conditions in the intertidal zone are the cause of an ample amount of dead macroinvertebrates, which constitute a food source for carrion-feeders. In the European Wadden Sea, this trophic guild includes decapod crustaceans and fish when the tide is in, while during nocturnal low tides the polychaete Phyllodoce mucosa is attracted in large numbers by dead mollusks, crabs or worms on the sediment surface. Within 10 s worms emerged to the surface, crawled as far as 15 m on mucus trails towards the carcass, sucked in tissue up to one-third of their own weight, and then quickly retreated to below the surface. Abundance of P. mucosa was highest in the lower intertidal zone and winter. The seaward high abundance pattern, however, did not continue into the shallow subtidal. In summer, few were attracted during daytime or when the tide was in. However, up to 447 worms aggregated at a single crushed mussel within 20 min at dusk during low-tide exposure. This study suggests that during winter carrion-feeding is an important trophic niche on cold-temperate, intertidal mud flats occupied by a phyllodocid polychaete that is segregated in feeding time from most other scavengers and benefits from cold-sensitive benthic invertebrates.

Marine Biology

6342475

10.1016/S1937-6448(08)01803-0

Giant siliceous spicules from the deep-sea glass sponge Monorhaphis chuni.

Only 13 years after realizing, during a repair of a telegraph cable pulled out from the deep sea, that the depth of the ocean is plentifully populated with a highly diverse fauna and flora, the Challenger expedition (1873-1876) treasured up a rich collection of vitreous sponges (Hexactinellida). They had been described by Schulze and represent the phylogenetically oldest class of siliceous sponges (phylum Porifera); they are eye-catching because of their distinct body plan, which relies on a filigree skeleton. It is constructed by an array of morphologically determined elements, the spicules. Soon after, during the German Deep Sea Expedition "Valdivia" (1898-1899), Schulze could describe the largest siliceous hexactinellid sponge on Earth, the up to 3-m high Monorhaphis chuni, which develops the equally largest bio-silica structure, the giant basal spicules (3 mx10 mm). Using these spicules as a model, basic knowledge on the morphology, formation, and development of the skeletal elements could be achieved. They are formed by a proteinaceous scaffold (composed of a 27-kDa protein), which mediates the formation of the siliceous lamellae, into which the proteins are encased. The high number of 800 of 5-10 microm thick lamellae is concentrically arranged around the axial canal. The silica matrix is composed of almost pure silicon oxide, providing it with unusually optophysical properties, which are superior to those of man-made waveguides. Experiments might suggest that the spicules function in vivo as a nonocular photoreception system. In addition, the spicules have exceptional mechanical properties, combining mechanical stability with strength and stiffness. Like demosponges, also the hexactinellids synthesize their silica enzymatically, via the enzyme silicatein (27-kDa protein). It is suggested that these basic insights will surely contribute to a further applied utilization and exploration of silica in bio-material/biomedical science.

International Review of Cell and Molecular Biology

205241696

10.1073/PNAS.0806604105

Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

Sea urchin larval spicules transform amorphous calcium carbonate (ACC) into calcite single crystals. The mechanism of transformation is enigmatic: the transforming spicule displays both amorphous and crystalline properties, with no defined crystallization front. Here, we use X-ray photoelectron emission spectromicroscopy with probing size of 40–200 nm. We resolve 3 distinct mineral phases: An initial short-lived, presumably hydrated ACC phase, followed by an intermediate transient form of ACC, and finally the biogenic crystalline calcite phase. The amorphous and crystalline phases are juxtaposed, often appearing in adjacent sites at a scale of tens of nanometers. We propose that the amorphous-crystal transformation propagates in a tortuous path through preexisting 40- to 100-nm amorphous units, via a secondary nucleation mechanism.

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

2050436

10.1038/SREP02617

Feeling Small: Exploring the Tactile Perception Limits

The human finger is exquisitely sensitive in perceiving different materials, but the question remains as to what length scales are capable of being distinguished in active touch. We combine material science with psychophysics to manufacture and haptically explore a series of topographically patterned surfaces of controlled wavelength, but identical chemistry. Strain-induced surface wrinkling and subsequent templating produced 16 surfaces with wrinkle wavelengths ranging from 300 nm to 90 μm and amplitudes between 7 nm and 4.5 μm. Perceived similarities of these surfaces (and two blanks) were pairwise scaled by participants, and interdistances among all stimuli were determined by individual differences scaling (INDSCAL). The tactile space thus generated and its two perceptual dimensions were directly linked to surface physical properties – the finger friction coefficient and the wrinkle wavelength. Finally, the lowest amplitude of the wrinkles so distinguished was approximately 10 nm, demonstrating that human tactile discrimination extends to the nanoscale.

Scientific Reports

528633

10.1242/JEB.029975

Surface tension propulsion of fungal spores

SUMMARY Most basidiomycete fungi actively eject their spores. The process begins with the condensation of a water droplet at the base of the spore. The fusion of the droplet onto the spore creates a momentum that propels the spore forward. The use of surface tension for spore ejection offers a new paradigm to perform work at small length scales. However, this mechanism of force generation remains poorly understood. To elucidate how fungal spores make effective use of surface tension, we performed a detailed mechanical analysis of the three stages of spore ejection: the transfer of energy from the drop to the spore, the work of fracture required to release the spore from its supporting structure and the kinetic energy of the spore after ejection. High-speed video imaging of spore ejection in Auricularia auricula and Sporobolomyces yeasts revealed that drop coalescence takes place over a short distance (∼5 μm) and energy transfer is completed in less than 4 μs. Based on these observations, we developed an explicit relation for the conversion of surface energy into kinetic energy during the coalescence process. The relation was validated with a simple artificial system and shown to predict the initial spore velocity accurately (predicted velocity: 1.2 m s–1; observed velocity: 0.8 m s–1 for A. auricula). Using calibrated microcantilevers, we also demonstrate that the work required to detach the spore from the supporting sterigma represents only a small fraction of the total energy available for spore ejection. Finally, our observations of this unique discharge mechanism reveal a surprising similarity with the mechanics of jumping in animals.

The Journal of Experimental Biology

16032014

10.1098/RSBL.2010.0993

Penguin heat-retention structures evolved in a greenhouse Earth

Penguins (Sphenisciformes) inhabit some of the most extreme environments on Earth. The 60+ Myr fossil record of penguins spans an interval that witnessed dramatic shifts in Cenozoic ocean temperatures and currents, indicating a long interplay between penguin evolution and environmental change. Perhaps the most celebrated example is the successful Late Cenozoic invasion of glacial environments by crown clade penguins. A major adaptation that allows penguins to forage in cold water is the humeral arterial plexus, a vascular counter-current heat exchanger (CCHE) that limits heat loss through the flipper. Fossil evidence reveals that the humeral plexus arose at least 49 Ma during a ‘Greenhouse Earth’ interval. The evolution of the CCHE is therefore unrelated to global cooling or development of polar ice sheets, but probably represents an adaptation to foraging in subsurface waters at temperate latitudes. As global climate cooled, the CCHE was key to invasion of thermally more demanding environments associated with Antarctic ice sheets.

Biology Letters

45633864

10.1007/BF02112137

Flow, flapping, and photosynthesis ofNereocystis leutkeana: a functional comparison of undulate and flat blade morphologies

A number of species of macroalagae possess a flat, strap-like blade morphology in habitats exposed to rapidly-moving water whereas those at protected sites have a wider, undulate blade shape. We have explored the functional consequences of flat, narrow vs. wide, undulate blade morphologies in the giant bull kelpNereocystis luetkeana. Our study focused on the behavior of blades in ambient water currents and the consequences of that behavior to breakage and to photosynthesis. In flowing water, the narrow, flat blades flap with lower amplitude and collapse together into a more streamlined bundle than do wide, undulate blades, and hence experience lower drag per blade area at a given flow velocity. If the algae at current-swept sites had ruffled blades, drag forces would sometimes be sufficient to break the stipes. However, flat blades in a streamlined bundle experience more self-shading than do undulate blades, which remain spread out in water currents. Thus, there is a morphological trade-off between reducing drag and reducing self-shading. Photosynthetic14C-HCO3 uptake rates decrease in slow flow when the boundary layer along the blade surface across which diffusion takes place is relatively thick. However, blade flapping, which stirs water near the blade surface, enhances carbon uptake rates in slow water currents for both the undulate and the flat morphologies.

Marine Biology

43857104

10.1126/SCIENCE.1116612

Directionally Controlled Fluorescence Emission in Butterflies

Recently developed, high-efficiency, light-emitting diodes use two-dimensional photonic crystals to enhance the extraction of otherwise internally trapped light and multilayer reflectors to control the direction of light emission. This work describes the characterization of a naturally evolved light-extraction system on the wing scales of a small group of Papilio butterflies. The efficient extraction of fluorescence from these scales is facilitated by a two-dimensional photonic crystal slab that uses a multilayer to help control emission direction. Its light-extraction function is analogous to that of the light-emitting diode.

Science

8747381

10.1073/PNAS.1317120111

Evidence that dimethyl sulfide facilitates a tritrophic mutualism between marine primary producers and top predators

Significance This study demonstrates that dimethyl sulfide, a chemical cue involved in global climate regulation, mediates a tritrophic mutualistic interaction between marine apex predators and primary producers. Our results imply that marine top predators play a critical role in maintaining both ocean health and global climate. Our results highlight the need for more collaboration and discussion between micro- and macroscale biologists working on global issues in the Southern Ocean. Tritrophic mutualistic interactions have been best studied in plant–insect systems. During these interactions, plants release volatiles in response to herbivore damage, which, in turn, facilitates predation on primary consumers or benefits the primary producer by providing nutrients. Here we explore a similar interaction in the Southern Ocean food web, where soluble iron limits primary productivity. Dimethyl sulfide has been studied in the context of global climate regulation and is an established foraging cue for marine top predators. We present evidence that procellariiform seabird species that use dimethyl sulfide as a foraging cue selectively forage on phytoplankton grazers. Their contribution of beneficial iron recycled to marine phytoplankton via excretion suggests a chemically mediated link between marine top predators and oceanic primary production.

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

53202938

10.1016/J.ANBEHAV.2009.10.010

Antipredatory properties of an animal architecture: how complex faecal cases thwart arthropod attack

Animals create a wide variety of structures to deal with abiotic and biotic challenges. We evaluated an intriguing structure whose function has never been thoroughly tested. Specifically, we evaluated the hypothesis that the body-enclosing ‘faecal case’ created and lived in by the immature stages of Neochlamisus leaf beetles reduces their risk of predation. We especially focus on the case of N. platani, which is externally covered with host-plant trichomes, and includes a distinct trichome-filled chamber (‘attic’) in the case apex. Here, we separately evaluated the effects of case, trichomes and attic on each of several behavioural stages of predator attack using N. platani and N. bimaculatus larvae and pupae. Three generalist predators (crickets, soldier bugs and lynx spiders) that represent different feeding strategies were used in our individual-level repeated observation behavioural trials. Results strongly demonstrated that the faecal case itself greatly reduced predation risk for all combinations of beetle species, life history stage and predator. Additional evidence indicated that both trichomes and attics further and independently reduced predation risk. Variation in results among treatments was also informative. For example, the capacity of faecal case components to reduce predation sometimes varied markedly among predators and between larval versus pupal life stages. Patterns of predator behaviour provided no evidence that caseless larvae have alternative means of defence. This study further presents a rare example of the co-option of a physical plant defence (trichomes) by an herbivore.

Animal Behaviour

29927841

10.1890/10-1239.1

The high cost of mutualism: effects of four species of East African ant symbionts on their myrmecophyte host tree.

Three recent meta-analyses of protective plant-ant mutualisms report a surprisingly weak relationship between herbivore protection and measured demographic benefits to ant-plants, suggesting high tolerance for herbivory, substantial costs of ant-mediated defense, and/or benefits that are realized episodically rather than continuously. Experimental manipulations of protective ant-plant associations typically last for less than a year, yet virtually all specialized myrmecophytes are long-lived perennials for which the costs and benefits of maintaining ant symbionts could accrue at different rates over the host's lifetime. To complement long-term monitoring studies, we experimentally excluded each of four ant symbionts from their long-lived myrmecophyte host trees (Acacia drepanolobium) for 4.5 years. Ant species varied in their effectiveness against herbivores and in their effects on intermediate-term growth and reproduction, but the level of herbivore protection provided was a poor predictor of the net impact they had on host trees. Removal of the three Crematogaster species resulted in cumulative gains in host tree growth and/or reproduction over the course of the experiment, despite the fact that two of those species significantly reduce chronic herbivore damage. In contrast, although T. penzigi is a relatively poor defender, the low cost of maintaining this ant symbiont apparently eliminated negative impacts on overall tree growth and reproduction, resulting in enhanced allocation to new branch growth by the final census. Acacia drepanolobium is evidently highly tolerant of herbivory by insects and small browsers, and the costs of maintaining Crematogaster colonies exceeded the benefits received during the study. No experimental trees were killed by elephants, but elephant damage was uniquely associated with reduced tree growth, and at least one ant species (C. mimosae) strongly deterred elephant browsing. We hypothesize that rare but catastrophic damage by elephants may be more important than chronic herbivory in maintaining the costly myrmecophyte habit in this system.

Ecology

205048789

10.1038/461047A

Structural biology: A channel with a twist

Mechanosensitive channels release tension in cell membranes by opening 'pressure relief' pores. The structure of a partially open channel suggests a gating mechanism and delivers an unexpected architectural twist. Mechanosensitive channels protect bacteria from osmotic shock by allowing ions to flow across the membrane in response to changes in membrane tension. MscL is one such channel with large conductance, which exhibits several intermediate states between its closed and open forms. The 3.8-Å crystal structure of the Staphylococcus aureus MscL has now been determined in a nonconductive, partially expanded and tetrameric form.

Nature

1150725

10.1073/PNAS.1216441109

Microstructured barbs on the North American porcupine quill enable easy tissue penetration and difficult removal

North American porcupines are well known for their specialized hairs, or quills that feature microscopic backward-facing deployable barbs that are used in self-defense. Herein we show that the natural quill’s geometry enables easy penetration and high tissue adhesion where the barbs specifically contribute to adhesion and unexpectedly, dramatically reduce the force required to penetrate tissue. Reduced penetration force is achieved by topography that appears to create stress concentrations along regions of the quill where the cross sectional diameter grows rapidly, facilitating cutting of the tissue. Barbs located near the first geometrical transition zone exhibit the most substantial impact on minimizing the force required for penetration. Barbs at the tip of the quill independently exhibit the greatest impact on tissue adhesion force and the cooperation between barbs in the 0–2 mm and 2–4 mm regions appears critical to enhance tissue adhesion force. The dual functions of barbs were reproduced with replica molded synthetic polyurethane quills. These findings should serve as the basis for the development of bio-inspired devices such as tissue adhesives or needles, trocars, and vascular tunnelers where minimizing the penetration force is important to prevent collateral damage.

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

210088215

10.1038/S41467-019-13660-X

Inhibiting bacterial cooperation is an evolutionarily robust anti-biofilm strategy

Bacteria commonly form dense biofilms encased in extracellular polymeric substances (EPS). Biofilms are often extremely tolerant to antimicrobials but their reliance on shared EPS may also be a weakness as social evolution theory predicts that inhibiting shared traits can select against resistance. Here we show that EPS of Salmonella biofilms is a cooperative trait whose benefit is shared among cells, and that EPS inhibition reduces both cell attachment and antimicrobial tolerance. We then compare an EPS inhibitor to conventional antimicrobials in an evolutionary experiment. While resistance against conventional antimicrobials rapidly evolves, we see no evolution of resistance to EPS inhibition. We further show that a resistant strain is outcompeted by a susceptible strain under EPS inhibitor treatment, explaining why resistance does not evolve. Our work suggests that targeting cooperative traits is a viable solution to the problem of antimicrobial resistance. Bacterial biofilms rely on shared extracellular polymeric substances (EPS) and are often highly tolerant to antibiotics. Here, the authors show in in vitro experiments that Salmonella does not evolve resistance to EPS inhibition because such strains are outcompeted by a susceptible strain under inhibitor treatment.

Nature Communications

7908760

10.1007/BF00384549

Dead leaves and fire survival in Southern African tree aloes

SummaryMany aloe species in southern Africa have stems clothed with a layer of persistent dead leaves. The degree of stem coverage is species-specific. The suggestion that persistent dead leaves have an insulatory function and are adaptive in fire-prone habitat was tested on Aloe ferox. Field surveys demonstrated a significant negative relationship between mortality and degree of stem coverage and laboratory studies confirmed the insulating properties of dead leaves. The distribution of southern African tree aloes supprts the prediction that bare-stemmed species would be confined to fire-free habitat whilst fully clothed species would occur in both fire-prone and fire-free habitat. The study suggests that harvesting of Aloe ferox leaves for medicinal purposes could result in significant mortality in fires.

Oecologia

44490101

10.1126/SCIENCE.1091288

Reflectins: The Unusual Proteins of Squid Reflective Tissues

A family of unusual proteins is deposited in flat, structural platelets in reflective tissues of the squid Euprymna scolopes. These proteins, which we have named reflectins, are encoded by at least six genes in three subfamilies and have no reported homologs outside of squids. Reflectins possess five repeating domains, which are highly conserved among members of the family. The proteins have a very unusual composition, with four relatively rare residues (tyrosine, methionine, arginine, and tryptophan) comprising ∼57% of a reflectin, and several common residues (alanine, isoleucine, leucine, and lysine) occurring in none of the family members. These protein-based reflectors in squids provide a marked example of nanofabrication in animal systems.

Science

10062174

10.1002/JMOR.10011

How do ants stick out their tongues?

The mouthparts are very important tools for almost any task performed by ants. In particular, the labiomaxillary complex is essential for food intake. In the present study we investigated the anatomical design of the labiomaxillary complex in various ant species, focusing on movement mechanisms. Six labial and six maxillary muscles with different functions control the several joints and ensure the proper performance of the labiomaxillary complex. According to our measurements of sarcomere lengths, muscle fiber lengths and diameters, and the relative muscle volumes, the labial and maxillary muscles feature rather slow than fast muscle characteristics and do not seem to be specialized for specific tasks. Since glossa protractor muscles are absent, the protraction of the glossa, the distal end of the labium, is a nonmuscular movement. By histological measurements of hemolymph volumes we could exclude a pressure‐driven mechanism. Additional experiments showed that, upon relaxation of the glossa retractor muscles, the glossa protracts elastically. This elastic mechanism possibly sets an upper limit to licking frequency, thus influencing food intake rates and ultimately foraging behavior. In contrast to many other elastic mechanisms among arthropods, glossa protraction in ants is based on a mechanism where elasticity works as an actual antagonist to muscles. We compared the design of the labiomaxillary complex of ants with that of the honeybee and suggest an elastic mechanism for glossa protraction in honeybees as well. J. Morphol. 254:39–52, 2002. © 2002 Wiley‐Liss, Inc.

Journal of Morphology

7870604

10.1104/PP.101.1.31

Correlation between the Circadian Rhythm of Resistance to Extreme Temperatures and Changes in Fatty Acid Composition in Cotton Seedlings

Fluctuations in fatty acid composition were examined in cotton (Gossypium hirsutum L. cv Deltapine 50) leaves during light-dark cycles of 12:12 h and under continuous light and were correlated to the rhythmic changes in chilling (5[deg]C) resistance (CR) and heat (53[deg]C) resistance (HR). The chilling-resistant and chilling-sensitive phases developed in the dark or the light period, respectively, and this rhythm persisted under continuous light for three cycles. The heat-resistant phase developed in the light period and an additional peak of HR occurred in the middle of the dark period. Under continuous light, only one peak of HR developed, lasting from the middle of the subjective night to the middle of the subjective day. The amounts of palmitic and oleic acids were constant during the light-dark cycle and under continuous light, but those of linoleic and linolenic acids fluctuated, attaining a high level in the middle of the dark period or the subjective night, and a low level in the middle of the light period or the subjective day. A low temperature of 20[deg]C induced CR and affected changes in fatty acid composition similar to those that occurred during the daily CR phase. A high temperature of 40[deg]C induced HR but did not affect changes in fatty acid composition. The results in their entirety show that the CR that develops rhythmically as well as the low-temperature-induced CR coincide with increased levels of polyunsaturated fatty acids. No correlation is found between changes in fatty acid composition and the HR that develops rhythmically or the high-temperature-induced HR.

Plant Physiology

17784911

10.1371/JOURNAL.PONE.0021114

A Unique Resource Mutualism between the Giant Bornean Pitcher Plant, Nepenthes rajah, and Members of a Small Mammal Community

The carnivorous pitcher plant genus Nepenthes grows in nutrient-deficient substrates and produce jug-shaped leaf organs (pitchers) that trap arthropods as a source of N and P. A number of Bornean Nepenthes demonstrate novel nutrient acquisition strategies. Notably, three giant montane species are engaged in a mutualistic association with the mountain treeshrew, Tupaia montana, in which the treeshrew defecates into the pitchers while visiting them to feed on nectar secretions on the pitchers' lids. Although the basis of this resource mutualism has been elucidated, many aspects are yet to be investigated. We sought to provide insights into the value of the mutualism to each participant. During initial observations we discovered that the summit rat, R. baluensis, also feeds on sugary exudates of N. rajah pitchers and defecates into them, and that this behavior appears to be habitual. The scope of the study was therefore expanded to assess to what degree N. rajah interacts with the small mammal community. We found that both T. montana and R. baluensis are engaged in a mutualistic interaction with N. rajah. T .montana visit pitchers more frequently than R. baluensis, but daily scat deposition rates within pitchers do not differ, suggesting that the mutualistic relationships are of a similar strength. This study is the first to demonstrate that a mutualism exists between a carnivorous plant species and multiple members of a small mammal community. Further, the newly discovered mutualism between R. baluensis and N. rajah represents only the second ever example of a multidirectional resource-based mutualism between a mammal and a carnivorous plant.

PLOS ONE

83772884

10.1002/J.1537-2197.1984.TB12506.X

ULTRASTRUCTURAL BASIS AND DEVELOPMENTAL CONTROL OF BLUE IRIDESCENCE IN SELAGINELLA LEAVES

American Journal of Botany

6191096

10.1007/BF00611243

Stationary underwater prey missed by reef herons,Egretta gularis: head position and light refraction at the moment of strike

SummaryThis paper attempts to verify the importance of spatial positioning of the eyes of reef heronsEgretta gularis schistacea, when coping with light refraction at the air-water interface. The herons' striking of prey, while their approach angle was restricted, was observed. (a) The herons' capture success in the restricted situation was markedly lower than in the unrestricted situation. (b) The points of strike (STR) in unsuccessful strikes differed from those of successful strikes, and from those of the unrestricted situation. (c) The larger the difference between the observed and the predicted ratio of prey depth to apparent prey depth, the higher the probability of missing a prey. These results support predictions of a model presented elsewhere (Katzir and Intrator 1987) that a heron will attempt to reach spatial positions at which prey's real depth and apparent depth are linearly correlated.

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

12685855

10.1126/SCIENCE.1096340

Honey Bee Nest Thermoregulation: Diversity Promotes Stability

A honey bee colony is characterized by high genetic diversity among its workers, generated by high levels of multiple mating by its queen. Few clear benefits of this genetic diversity are known. Here we show that brood nest temperatures in genetically diverse colonies (i.e., those sired by several males) tend to be more stable than in genetically uniform ones (i.e., those sired by one male). One reason this increased stability arises is because genetically determined diversity in workers' temperature response thresholds modulates the hive-ventilating behavior of individual workers, preventing excessive colony-level responses to temperature fluctuations.

Science

7484330

10.1007/S00114-005-0069-7

Decay of cacti and carbon cycling

Cacti contain large quantities of Ca-oxalate biominerals, with C derived from atmospheric CO2. Their death releases these biominerals into the environment, which subsequently transform to calcite via a monohydrocalcite intermediate. Here, the fate of Ca-oxalates released by plants in arid environments is investigated. This novel and widespread form of biomineralization has unexpected consequences on C cycling and calcite accumulation in areas with large numbers of cacti. The magnitude of this mineralization is revealed by studying the large columnar cactus Carnegiea gigantea (Engelm.) Britton and Rose in southwestern Arizona (locally called the saguaro). A large C. gigantea contains on the order of 1×105 g of the Ca-oxalate weddellite—CaC2O4·2H2O. In areas with high C. gigantea density, there is an estimated 40 g Catm m−2 sequestered in Ca-oxalates. Following the death of the plant, the weddellite transforms to calcite on the order to 10–20 years. In areas with high saguaro density, there is an estimated release of up to 2.4 g calcite m−2 year−1 onto the desert soil. Similar transformation mechanisms occur with the Ca-oxalates that are abundant in the majority of cacti. Thus, the total atmospheric C returned to the soil of areas with a high number density of cacti is large, suggesting that there may be a significant long-term accumulation of atmospheric C in these soils derived from Ca-oxalate biominerals. These findings demonstrate that plant decay in arid environments may have locally significant impacts on the Ca and inorganic C cycles.

Naturwissenschaften

14544539

10.1039/B902775K

Self-assembly of amorphous biophotonic nanostructures by phase separation

Some of the most vivid colors in the animal kingdom are created not by pigments, but by wavelength-selective scattering of light from nanostructures. Here we investigate quasi-ordered nanostructures of avian feather barbs which produce vivid non-iridescent colors. These β-keratin and air nanostructures are found in two basic morphologies: tortuous channels and amorphous packings of spheres. Each class of nanostructure is isotropic and has a pronounced characteristic length scale of variation in composition. These local structural correlations lead to strong backscattering over a narrow range of optical frequencies and little variation with angle of incidence. Such optical properties play important roles in social and sexual communication. To be effective, birds need to precisely control the development of these nanoscale structures, yet little is known about how they grow. We hypothesize that multiple lineages of birds have convergently evolved to exploit phase separation and kinetic arrest to self-assemble spongy color-producing nanostructures in feather barbs. Observed avian nanostructures are strikingly similar to those self-assembled during the phase separation of fluid mixtures; the channel and sphere morphologies are characteristic of phase separation by spinodal decomposition and nucleation and growth, respectively. These unstable structures are locked-in by the kinetic arrest of the β-keratin matrix, likely through the entanglement or cross-linking of supermolecular β-keratin fibers. Using the power of self-assembly, birds can robustly realize a diverse range of nanoscopic morphologies with relatively small physical and chemical changes during feather development.

Soft Matter

15707273

10.1007/S00332-002-0513-1

A Dynamical System for Plant Pattern Formation: A Rigorous Analysis

SummaryWe present a rigorous mathematical analysis of a discrete dynamical system modeling plant pattern formation. In this model, based on the work of physicists Douady and Couder, fixed points are the spiral or helical lattices often occurring in plants. The frequent occurrence of the Fibonacci sequence in the number of visible spirals is explained by the stability of the fixed points in this system, as well as by the structure of their bifurcation diagram. We provide a detailed study of this diagram.

Journal of Nonlinear Science

206509131

10.1126/SCIENCE.1147241

Mussel-Inspired Surface Chemistry for Multifunctional Coatings

We report a method to form multifunctional polymer coatings through simple dip-coating of objects in an aqueous solution of dopamine. Inspired by the composition of adhesive proteins in mussels, we used dopamine self-polymerization to form thin, surface-adherent polydopamine films onto a wide range of inorganic and organic materials, including noble metals, oxides, polymers, semiconductors, and ceramics. Secondary reactions can be used to create a variety of ad-layers, including self-assembled monolayers through deposition of long-chain molecular building blocks, metal films by electroless metallization, and bioinert and bioactive surfaces via grafting of macromolecules.

Science

10263928

10.1007/S00425-008-0766-5

Photoprotection of green plants: a mechanism of ultra-fast thermal energy dissipation in desiccated lichens

In order to survive sunlight in the absence of water, desiccation-tolerant green plants need to be protected against photooxidation. During drying of the chlorolichen Cladonia rangiformis and the cyanolichen Peltigera neckeri, chlorophyll fluorescence decreased and stable light-dependent charge separation in reaction centers of the photosynthetic apparatus was lost. The presence of light during desiccation increased loss of fluorescence in the chlorolichen more than that in the cyanolichen. Heating of desiccated Cladonia thalli, but not of Peltigera thalli, increased fluorescence emission more after the lichen had been dried in the light than after drying in darkness. Activation of zeaxanthin-dependent energy dissipation by protonation of the PsbS protein of thylakoid membranes was not responsible for the increased loss of chlorophyll fluorescence by the chlorolichen during drying in the light. Glutaraldehyde inhibited loss of chlorophyll fluorescence during drying. Desiccation-induced loss of chlorophyll fluorescence and of light-dependent charge separation are interpreted to indicate activation of a highly effective mechanism of photoprotection in the lichens. Activation is based on desiccation-induced conformational changes of a pigment–protein complex. Absorbed light energy is converted into heat within a picosecond or femtosecond time domain. When present during desiccation, light interacts with the structural changes of the protein providing increased photoprotection. Energy dissipation is inactivated and structural changes are reversed when water becomes available again. Reversibility of ultra-fast thermal dissipation of light energy avoids photo-damage in the absence of water and facilitates the use of light for photosynthesis almost as soon as water becomes available.

Planta

17787568

10.1038/NRMICRO2073

A new perspective on radiation resistance based on Deinococcus radiodurans

In classical models of radiation toxicity, DNA is the molecule that is most affected by ionizing radiation (IR). However, recent data show that the amount of protein damage caused during irradiation of bacteria is better related to survival than to DNA damage. In this Opinion article, a new model is presented in which proteins are the most important target in the hierarchy of macromolecules affected by IR. A first line of defence against IR in extremely radiation-resistant bacteria might be the accumulation of manganese complexes, which can prevent the production of iron-dependent reactive oxygen species. This would allow an irradiated cell to protect sufficient enzymatic activity needed to repair DNA and survive.

Nature Reviews Microbiology

28195958

10.1007/S00253-008-1778-6

Conversion of dibenzothiophene by the mushrooms Agrocybe aegerita and Coprinellus radians and their extracellular peroxygenases

The conversion of the heterocycle dibenzothiophene (DBT) by the agaric basidiomycetes Agrocybe aegerita and Coprinellus radians was studied in vivo and in vitro with whole cells and with purified extracellular peroxygenases, respectively. A. aegerita oxidized DBT (110 μM) by 100% within 16 days into eight different metabolites. Among the latter were mainly S-oxidation products (DBT sulfoxide, DBT sulfone) and in lower amounts, ring-hydroxylation compounds (e.g., 2-hydroxy-DBT). C. radians converted about 60% of DBT into DBT sulfoxide and DBT sulfone as the sole metabolites. In vitro tests with purified peroxygenases were performed to compare the product pattern with the metabolites formed in vivo. Using ascorbic acid as radical scavenger, a total of 19 and seven oxygenation products were detected after DBT conversion by the peroxygenases of A. aegerita (AaP) and C. radians (CrP), respectively. Whereas ring hydroxylation was favored over S-oxidation by AaP (again 2-hydroxy-DBT was identified), CrP formed DBT sulfoxide as major product. This finding suggests that fungal peroxygenases can considerably differ in their catalytic properties. Using H218O2, the origin of oxygen was proved to be the peroxide. Based on these results, we propose that extracellular peroxygenases may be involved in the oxidation of heterocycles by fungi also under natural conditions.

Applied Microbiology and Biotechnology

120154022

10.1063/1.3148363

A reliable method of manufacturing metallic hierarchical superhydrophobic surfaces

A method of manufacturing hierarchical metallic surfaces demonstrating superhydrophobic properties is presented. The surfaces showed apparent contact angles as high as 153° and sliding angles of 10° for 50–100 μl droplets. The Cassie-like model [A. B. D. Cassie and S. Baxter, Trans. Faraday Soc. 40, 546 (1944)], considering the hierarchical topography of the relief, predicts apparent contact angles in a satisfactory agreement with the measured values.

Applied Physics Letters

2952266

10.1242/JEB.031880

Ant search strategies after interrupted tandem runs

SUMMARY Tandem runs are a form of recruitment in ants. During a tandem run, a single leader teaches one follower the route to important resources such as sources of food or better nest sites. In the present study, we investigate what tandem leaders and followers do, in the context of nest emigration, if their partner goes missing. Our experiments involved removing either leaders or followers at set points during tandem runs. Former leaders first stand still and wait for their missing follower but then most often proceed alone to the new nest site. By contrast, former followers often first engage in a Brownian search, for almost exactly the time that their former leader should have waited for them, and then former followers switch to a superdiffusive search. In this way, former followers first search their immediate neighbourhood for their lost leader before becoming ever more wide ranging so that in the absence of their former leader they can often find the new nest, re-encounter the old one or meet a new leader. We also show that followers gain useful information even from incomplete tandem runs. These observations point to the important principle that sophisticated communication behaviours may have evolved as anytime algorithms, i.e. procedures that are beneficial even if they do not run to completion.

The Journal of Experimental Biology

44935806

10.1016/J.JPLPH.2005.11.007

A lichen protected by a super-hydrophobic and breathable structure.

A species of lichen, Lecanora conizaeoides, is shown to be super-hydrophobic. It uses a combination of hydrophobic compounds and multi-layered roughness to shed water effectively. This is combined with gas channels to produce a biological analogue of a waterproof, breathable garment. The particular lichen grows mostly during wet seasons and is unusually resistant to acid rain [Hauck, M., 2003. The Bryologist 106(2), 257-269; Honegger, R., 1998. Lichenologist 30(3),193-212]. The waterproof, breathable surface allows this lichen to photosynthesise when other species are covered with a layer of water. In addition, rainwater runs off the surface of the organism, reducing its intake of water from above and probably contributing to its resistance to acid rain.

Journal of Plant Physiology

4995837

10.1017/S0022112005007925

Passive propulsion in vortex wakes

A dead fish is propelled upstream when its flexible body resonates with oncoming vortices formed in the wake of a bluff cylinder, despite being well outside the suction region of the cylinder. Within this passive propulsion mode, the body of the fish extracts sufficient energy from the oncoming vortices to develop thrust to overcome its own drag. In a similar turbulent wake and at roughly the same distance behind a bluff cylinder, a passively mounted high-aspect-ratio foil is also shown to propel itself upstream employing a similar flow energy extraction mechanism. In this case, mechanical energy is extracted from the flow at the same time that thrust is produced. These results prove experimentally that, under proper conditions, a body can follow at a distance or even catch up to another upstream body without expending any energy of its own. This observation is also significant in the development of low-drag energy harvesting devices, and in the energetics of fish dwelling in flowing water and swimming behind wake-forming obstacles.

Journal of Fluid Mechanics

122859389

10.1063/1.3486115

Biologically inspired humidity sensor based on three-dimensional photonic crystals

This letter presents a biomimetic humidity sensor inspired by the humidity-dependent color change observed in the cuticle of the Hercules beetle. A thin-film-type humidity sensor with nanoporous structures (three-dimensional photonic crystals) mimicking the spongy multilayer in the beetles was designed and fabricated using the colloidal templating method and a hydrophilic surface treatment. The visible color of the fabricated humidity sensor changes from blue-green to red as the environmental humidity increases. The wavelength of reflected light that is predicted by Bragg’s equation considering the effect of water absorption shows a good agreement with experimental results.

Applied Physics Letters

15735494

10.1242/JEB.032615

Enhanced visual fields in hammerhead sharks

SUMMARY Several factors that influence the evolution of the unusual head morphology of hammerhead sharks (family Sphyrnidae) are proposed but few are empirically tested. In this study we tested the ‘enhanced binocular field’ hypothesis (that proposes enhanced frontal binocularity) by comparison of the visual fields of three hammerhead species: the bonnethead shark, Sphyrna tiburo, the scalloped hammerhead shark, Sphyrna lewini, and the winghead shark, Eusphyra blochii, with that of two carcharhinid species: the lemon shark, Negaprion brevirostris, and the blacknose shark, Carcharhinus acronotus. Additionally, eye rotation and head yaw were quantified to determine if species compensate for large blind areas anterior to the head. The winghead shark possessed the largest anterior binocular overlap (48 deg.) and was nearly four times larger than that of the lemon (10 deg.) and blacknose (11 deg.) sharks. The binocular overlap in the scalloped hammerhead sharks (34 deg.) was greater than the bonnethead sharks (13 deg.) and carcharhinid species; however, the bonnethead shark did not differ from the carcharhinids. These results indicate that binocular overlap has increased with lateral head expansion in hammerhead sharks. The hammerhead species did not demonstrate greater eye rotation in the anterior or posterior direction. However, both the scalloped hammerhead and bonnethead sharks exhibited greater head yaw during swimming (16.9 deg. and 15.6 deg., respectively) than the lemon (15.1 deg.) and blacknose (15.0 deg.) sharks, indicating a behavioral compensation for the anterior blind area. This study illustrates the larger binocular overlap in hammerhead species relative to their carcharhinid sister taxa and is consistent with the ‘enhanced binocular field’ hypothesis.

The Journal of Experimental Biology

84120382

10.1675/1524-4695(2005)028[0019:FAFBOT]2.0.CO;2

Food and Feeding Behavior of the Black-faced Spoonbill

Abstract Feeding Black-faced Spoonbills (Platalea minor) were studied in four main areas along the coasts of South Korea, Taiwan, China and Vietnam. They fed on nekton, mainly fish and shrimps, varying in length between 2-21 cm that were caught by sweeping the bill in the water. The feeding behavior of a spoonbill is a chain of feeding and inter-feeding bouts. Each feeding bout started by putting the bill into the water and ended when the bill was taken out and any prey captured was swallowed. The times between feeding bouts were short and no or few steps were made. In a complete feeding bout, up to three functional phases were distinguished. These were successively (1) the attempt to locate a prey, (2) the attempt to catch the located prey, (3) the handling and swallowing of the prey. A feeding bout could end in any phase. A total of 1,684 feeding bouts were recorded of which 65% ended with swallowing prey. The mean outcome was 45.4 small (<5 cm long) and 1.3 large (>5 cm long) prey per 10 min. Tentative measurements indicated that a feeding spoonbill walked on average 3.87 m per 10 s, during which time the bill made 15.7 sweeps with a bill velocity of 5.8 km.h-1, meanwhile testing about 17% of the area within reach of their bill for the presence of food. Feeding by Black-faced Spoonbills often looked chaotic because they usually walk all over the feeding site at a variable speed, while showing a large variety of actions especially when large prey is present. However, analyses of the observations show that they behave efficiently and reduce time and energy spent in feeding in several ways, including giving-up times not much longer than the duration of bouts with success, pursuing only large prey, ceasing feeding and starting to rest or going to another site when no prey is caught in 5-10 min. With their tactile way of feeding on invisible prey, they also behaved efficiently by consuming all detected prey that could be caught and swallowed.

Waterbirds

8053131

10.1073/PNAS.1003599107

Filtration of submicrometer particles by pelagic tunicates

Salps are common in oceanic waters and have higher per-individual filtration rates than any other zooplankton filter feeder. Although salps are centimeters in length, feeding via particle capture occurs on a fine, mucous mesh (fiber diameter d ∼0.1 μm) at low velocity (U = 1.6 ± 0.6 cm·s−1, mean ± SD) and is thus a low Reynolds-number (Re ∼10−3) process. In contrast to the current view that particle encounter is dictated by simple sieving of particles larger than the mesh spacing, a low-Re mathematical model of encounter rates by the salp feeding apparatus for realistic oceanic particle-size distributions shows that submicron particles, due to their higher abundances, are encountered at higher rates (particles per time) than larger particles. Data from feeding experiments with 0.5-, 1-, and 3-μm diameter polystyrene spheres corroborate these findings. Although particles larger than 1 μm (e.g., flagellates, small diatoms) represent a larger carbon pool, smaller particles in the 0.1- to 1-μm range (e.g., bacteria, Prochlorococcus) may be more quickly digestible because they present more surface area, and we find that particles smaller than the mesh size (1.4 μm) can fully satisfy salp energetic needs. Furthermore, by packaging submicrometer particles into rapidly sinking fecal pellets, pelagic tunicates can substantially change particle-size spectra and increase downward fluxes in the ocean.

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

952992

10.1073/PNAS.0707198104

Grass roots chemistry: meta-Tyrosine, an herbicidal nonprotein amino acid

Fine fescue grasses displace neighboring plants by depositing large quantities of an aqueous phytotoxic root exudate in the soil rhizosphere. Via activity-guided fractionation, we have isolated and identified the nonprotein amino acid m-tyrosine as the major active component. m-Tyrosine is significantly more phytotoxic than its structural isomers o- and p-tyrosine. We show that m-tyrosine exposure results in growth inhibition for a wide range of plant species and propose that the release of this nonprotein amino acid interferes with root development of competing plants. Acid hydrolysis of total root protein from Arabidopsis thaliana showed incorporation of m-tyrosine, suggesting this as a possible mechanism of phytotoxicity. m-Tyrosine inhibition of A. thaliana root growth is counteracted by exogenous addition of protein amino acids, with phenylalanine having the most significant effect. The discovery of m-tyrosine, as well as a further understanding of its mode(s) of action, could lead to the development of biorational approaches to weed control.

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

6894012

10.1023/A:1020587206351

Biogeochemistry and microbial ecology of methane oxidation in anoxic environments: a review

Evidence supporting a key role for anaerobic methane oxidation in the global methane cycle is reviewed. Emphasis is on recent microbiological advances. The driving force for research on this process continues to be the fact that microbial communities intercept and consume methane from anoxic environments, methane that would otherwise enter the atmosphere. Anaerobic methane oxidation is biogeochemically important because methane is a potent greenhouse gas in the atmosphere and is abundant in anoxic environments. Geochemical evidence for this process has been observed in numerous marine sediments along the continental margins, in methane seeps and vents, around methane hydrate deposits, and in anoxic waters. The anaerobic oxidation of methane is performed by at least two phylogenetically distinct groups of archaea, the ANME-1 and ANME-2. These archaea are frequently observed as consortia with sulfate-reducing bacteria, and the metabolism of these consortia presumably involves a syntrophic association based on interspecies electron transfer. The archaeal member of a consortium apparently oxidizes methane and shuttles reduced compounds to the sulfate-reducing bacteria. Despite recent advances in understanding anaerobic methane oxidation, uncertainties still remain regarding the nature and necessity of the syntrophic association, the biochemical pathway of methane oxidation, and the interaction of the process with the local chemical and physical environment. This review will consider the microbial ecology and biogeochemistry of anaerobic methane oxidation with a special emphasis on the interactions between the responsible organisms and their environment.

Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology

1066446

10.1152/AJPREGU.1993.265.6.R1339

Interaction between temperature and hypoxia in the alligator.

Hypoxia elicits behavioral hypothermia in alligators. Under normoxic conditions, the selected body temperature is 27.8 +/- 1.2 degrees C. However, when inspired O2 is lowered to 4%, selected body temperature decreases to 15.4 +/- 1.0 degrees C. The threshold for the behavioral hypothermia is between 4 and 5% inspired O2, the lowest threshold measured so far in terrestrial vertebrates. This study assessed the physiological significance of the behavioral hypothermia. The body temperature was clamped at 15, 25, and 35 degrees C for measurements of ventilation, blood gases, metabolic rate, plasma lactate, and acid-base status. Hypoxia-induced changes in ventilation, acid-base status, oxygen consumption, and lactate were proportional to body temperature, being pronounced at 35 degrees C, less at 25 degrees C, and absent at 15 degrees C. The correlation between selected body temperature under severe hypoxia and the measured parameters show that behavioral hypothermia is a beneficial response to hypoxia in alligators.

American Journal of Physiology-regulatory Integrative and Comparative Physiology

28019419

10.1021/JA057973P

Ladder polyether synthesis via epoxide-opening cascades using a disappearing directing group.

The combination of a trimethylsilyl group, a Brønsted base, a fluoride source, and a hydroxylic solvent enables the first construction of the tetrad of tetrahydropyran rings found in the majority of the ladder polyether natural products by way of a cascade of epoxide-opening events that emulates the final step of Nakanishi's proposed biosynthetic pathway. The trimethylsilyl group disappears during the course of the cascade, and thus these are the first epoxide ring-opening cascades that afford ladder polyether subunits containing no directing groups at the end of the cascade.

Journal of the American Chemical Society

53230212

10.1021/ACS.CHEMREV.7B00627

Nanocellulose, a Versatile Green Platform: From Biosources to Materials and Their Applications.

With increasing environmental and ecological concerns due to the use of petroleum-based chemicals and products, the synthesis of fine chemicals and functional materials from natural resources is of great public value. Nanocellulose may prove to be one of the most promising green materials of modern times due to its intrinsic properties, renewability, and abundance. In this review, we present nanocellulose-based materials from sourcing, synthesis, and surface modification of nanocellulose, to materials formation and applications. Nanocellulose can be sourced from biomass, plants, or bacteria, relying on fairly simple, scalable, and efficient isolation techniques. Mechanical, chemical, and enzymatic treatments, or a combination of these, can be used to extract nanocellulose from natural sources. The properties of nanocellulose are dependent on the source, the isolation technique, and potential subsequent surface transformations. Nanocellulose surface modification techniques are typically used to introduce either charged or hydrophobic moieties, and include amidation, esterification, etherification, silylation, polymerization, urethanization, sulfonation, and phosphorylation. Nanocellulose has excellent strength, high Young's modulus, biocompatibility, and tunable self-assembly, thixotropic, and photonic properties, which are essential for the applications of this material. Nanocellulose participates in the fabrication of a large range of nanomaterials and nanocomposites, including those based on polymers, metals, metal oxides, and carbon. In particular, nanocellulose complements organic-based materials, where it imparts its mechanical properties to the composite. Nanocellulose is a promising material whenever material strength, flexibility, and/or specific nanostructuration are required. Applications include functional paper, optoelectronics, and antibacterial coatings, packaging, mechanically reinforced polymer composites, tissue scaffolds, drug delivery, biosensors, energy storage, catalysis, environmental remediation, and electrochemically controlled separation. Phosphorylated nanocellulose is a particularly interesting material, spanning a surprising set of applications in various dimensions including bone scaffolds, adsorbents, and flame retardants and as a support for the heterogenization of homogeneous catalysts.

Chemical Reviews

38833738

10.1146/ANNUREV.MICRO.55.1.625

Hydrophobins: multipurpose proteins.

Class I and class II hydrophobins are small secreted fungal proteins that play a role in a broad range of processes in the growth and development of filamentous fungi. For instance, they are involved in the formation of aerial structures and in the attachment of hyphae to hydrophobic surfaces. The mechanisms by which hydrophobins fulfill these functions are based on their property to self-assemble at hydrophilic-hydrophobic interfaces into a 10 nm-thin highly amphipathic film. Complementation studies have shown that class I hydrophobins belong to a closely related group of morphogenetic proteins, but that they have evolved to function at specific interfaces. Recent evidence indicates that hydrophobins do not only function by self-assembly. Monomeric hydrophobin has been implicated in cell-wall assembly, but the underlying mechanism is not yet clear. In addition, hydrophobin monomers could act as toxins and elicitors.

Annual Review of Microbiology

25377545

10.1007/S00425-001-0718-9

Micromechanics of plant tissues beyond the linear-elastic range

Abstract. We investigated the relation between cell wall structure and the resulting mechanical characteristics of different plant tissues. Special attention was paid to the mechanical behaviour beyond the linear-elastic range, the underlying micromechanical processes and the fracture characteristics. The previously proposed model of reorientation and slippage of the cellulose microfibrils in the cell wall [H.-CH. Spatz et al. (1999) J Exp Biol 202:3269–3272) was supported and is here refined, using measurements of the changes in microfibrillar angle during straining. Our model explains the widespread phenomenon of stress-strain curves with two linear portions of different slope and sheds light on the micromechanical processes involved in viscoelasticity and plastic yield. We also analysed the velocity dependence of viscoelasticity under the perspective of the Kelvin model, resolving the measured viscoelasticity into functions of a velocity-dependent and a velocity-independent friction. The influence of lignin on the above-mentioned mechanical properties was examined by chemical lignin extraction from tissues of Aristolochia macrophylla Lam. and by the use of transgenic plants of Arabidopsis thaliana (L.) Heynh. with reduced lignin content. Additionally, the influence of extraction of hemicelluloses on the mechanical properties was investigated as well as a cell wall mutant of Arabidopsis with an altered configuration of the cellulose microfibrils.

Planta

22502219

10.1002/JMOR.10974

Finite element modeling of shell shape in the freshwater turtle Pseudemys concinna reveals a trade‐off between mechanical strength and hydrodynamic efficiency

Aquatic species can experience different selective pressures on morphology in different flow regimes. Species inhabiting lotic regimes often adapt to these conditions by evolving low‐drag (i.e., streamlined) morphologies that reduce the likelihood of dislodgment or displacement. However, hydrodynamic factors are not the only selective pressures influencing organismal morphology and shapes well suited to flow conditions may compromise performance in other roles. We investigated the possibility of morphological trade‐offs in the turtle Pseudemys concinna. Individuals living in lotic environments have flatter, more streamlined shells than those living in lentic environments; however, this flatter shape may also make the shells less capable of resisting predator‐induced loads. We tested the idea that “lotic” shell shapes are weaker than “lentic” shell shapes, concomitantly examining effects of sex. Geometric morphometric data were used to transform an existing finite element shell model into a series of models corresponding to the shapes of individual turtles. Models were assigned identical material properties and loaded under identical conditions, and the stresses produced by a series of eight loads were extracted to describe the strength of the shells. “Lotic” shell shapes produced significantly higher stresses than “lentic” shell shapes, indicating that the former is weaker than the latter. Females had significantly stronger shell shapes than males, although these differences were less consistent than differences between flow regimes. We conclude that, despite the potential for many‐to‐one mapping of shell shape onto strength, P. concinna experiences a trade‐off in shell shape between hydrodynamic and mechanical performance. This trade‐off may be evident in many other turtle species or any other aquatic species that also depend on a shell for defense. However, evolution of body size may provide an avenue of escape from this trade‐off in some cases, as changes in size can drastically affect mechanical performance while having little effect on hydrodynamic performance. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.

Journal of Morphology

2602258

10.1104/PP.104.046664

Sodium Transporters in Plants. Diverse Genes and Physiological Functions1

Soil salinity represents an increasing threat to agricultural production. High sodium (Na+) concentrations in soils are toxic to most higher plants. More than 40% of irrigated lands worldwide show increased salt levels. Several studies have shown that under saline conditions, Na+ influx into root

Plant Physiology

1784211

10.1371/JOURNAL.PONE.0026490

Why Do Woodpeckers Resist Head Impact Injury: A Biomechanical Investigation

Head injury is a leading cause of morbidity and death in both industrialized and developing countries. It is estimated that brain injuries account for 15% of the burden of fatalities and disabilities, and represent the leading cause of death in young adults. Brain injury may be caused by an impact or a sudden change in the linear and/or angular velocity of the head. However, the woodpecker does not experience any head injury at the high speed of 6–7 m/s with a deceleration of 1000 g when it drums a tree trunk. It is still not known how woodpeckers protect their brain from impact injury. In order to investigate this, two synchronous high-speed video systems were used to observe the pecking process, and the force sensor was used to measure the peck force. The mechanical properties and macro/micro morphological structure in woodpecker's head were investigated using a mechanical testing system and micro-CT scanning. Finite element (FE) models of the woodpecker's head were established to study the dynamic intracranial responses. The result showed that macro/micro morphology of cranial bone and beak can be recognized as a major contributor to non-impact-injuries. This biomechanical analysis makes it possible to visualize events during woodpecker pecking and may inspire new approaches to prevention and treatment of human head injury.

PLOS ONE

10328521

10.1017/S0033583503003883

Chaperonin-mediated protein folding: fate of substrate polypeptide

1. Chaperonin action – an overview 230 2. Polypeptide binding – an essential action 235 3. Recognition of non-native polypeptide – role of hydrophobicity 236 4. Crystallographic analyses of peptide binding 237 5. Topology and secondary and tertiary structure of bound substrate polypeptide – fluorescence, hydrogen exchange and NMR studies 239 6. Binding by GroEL associated with a putative unfolding action 242 7. A potential action of substrate unfolding driven by ATP/GroES binding 245 8. Folding in theciscavity 247 9. GroEL–GroES-mediated folding of larger substrate proteins by atransmechanism 249 10. Prospects for resolving the conformations and fate of polypeptide in the chaperonin reaction 251 11. References 252 Chaperonins are megadalton ring assemblies that mediate essential ATP-dependent assistance of protein folding to the native state in a variety of cellular compartments, including the mitochondrial matrix, the eukaryotic cytosol, and the bacterial cytoplasm. Structural studies of the bacterial chaperonin, GroEL, both alone and in complex with its co-chaperonin, GroES, have resolved the states of chaperonin that bind and fold non-native polypeptides. Functional studies have resolved the action of ATP binding and hydrolysis in driving the GroEL–GroES machine through its folding-active and binding-active states, respectively. Yet the exact fate of substrate polypeptide during these steps is only poorly understood. For example, while binding involves multivalent interactions between hydrophobic side-chains facing the central cavity of GroEL and exposed hydrophobic surfaces of the non-native protein, the structure of any polypeptide substrate while bound to GroEL remains unknown. It is also unclear whether binding to an open GroEL ring is accompanied by structural changes in the non-native substrate, in particular whether there is an unfolding action. As a polypeptide-bound ring becomes associated with GroES, do the large rigid-body movements of the GroEL apical domains serve as another source of a potential unfolding action? Regarding the encapsulated folding-active state, how does the central cavity itself influence the folding trajectory of a substrate? Finally, how do GroEL and GroES serve, as recently recognized, to assist the folding of substrates too large to be encapsulated inside the machine? Here, such questions are addressed with the findings available to date, and means of further resolving the states of chaperonin-associated polypeptide are discussed.

Quarterly Reviews of Biophysics

39794768

10.1002/IBD.20633

Helminths and the IBD hygiene hypothesis

&NA; Helminths are parasitic animals that have evolved over 100,000,000 years to live in the intestinal track or other locations of their hosts. Colonization of humans with these organisms was nearly universal until the early 20th century. More than 1,000,000,000 people in less developed countries carry helminths even today. Helminths must quell their host's immune system to successfully colonize. It is likely that helminths sense hostile changes in the local host environment and take action to control such responses. Inflammatory bowel disease (IBD) probably results from an inappropriately vigorous immune response to contents of the intestinal lumen. Environmental factors strongly affect the risk for IBD. People living in less developed countries are protected from IBD. The “IBD hygiene hypothesis” states that raising children in extremely hygienic environments negatively affects immune development, which predisposes them to immunological diseases like IBD later in life. Modern day absence of exposure to intestinal helminths appears to be an important environmental factor contributing to development of these illnesses. Helminths interact with both host innate and adoptive immunity to stimulate immune regulatory circuitry and to dampen effector pathways that drive aberrant inflammation. The first prototype worm therapies directed against immunological diseases are now under study in the United States and various countries around the world. Additional studies are in the advanced planning stage.

Inflammatory Bowel Diseases

25255045

10.3732/AJB.1000261

Effect of natural root grafting on growth response of jack pine (Pinus banksiana; Pinaceae).

PREMISE OF STUDY Trees are traditionally considered as distinct entities even though they can share a communal root system through root grafts, which are morphological unions between two or more roots. Little is known regarding the ecological significance of natural root grafting, but because grafted trees can share resources and secondary compounds, growth of linked trees can be affected directly by the presence of root grafts. Traditional forest ecology concepts may have to be revised to include direct interactions between connected trees. METHODS We hydraulically excavated six 30-50-m(2) plots (three natural stands and three plantations). We measured yearly radial growth and determined the influence of root grafting on radial growth of grafted trees. KEY RESULTS During periods of root graft formation, root grafting tended to reduce radial growth of jack pine trees, after which growth generally increased. The influence of root grafting on growth was more significant in natural stands, where root grafting was more frequent than in plantations. CONCLUSIONS These results suggest that root grafting initially is an energetically costly process but that it is afterward nonprejudicial and maybe beneficial to tree growth. The use of a communal root system allows for a maximum use of resources by redistributing them among trees, leading to increased tree growth.

American Journal of Botany

38895429

10.1073/PNAS.0605183104

Nuthatches eavesdrop on variations in heterospecific chickadee mobbing alarm calls

Many animals recognize the alarm calls produced by other species, but the amount of information they glean from these eavesdropped signals is unknown. We previously showed that black-capped chickadees (Poecile atricapillus) have a sophisticated alarm call system in which they encode complex information about the size and risk of potential predators in variations of a single type of mobbing alarm call. Here we show experimentally that red-breasted nuthatches (Sitta canadensis) respond appropriately to subtle variations of these heterospecific “chick-a-dee” alarm calls, thereby evidencing that they have gained important information about potential predators in their environment. This study demonstrates a previously unsuspected level of discrimination in intertaxon eavesdropping.

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

14114995

10.1242/JEB.036947

The role of granules within viscous capture threads of orb-weaving spiders

SUMMARY Sticky viscous prey capture threads form the spiral elements of spider orb-webs and are responsible for retaining insects that strike a web. These threads are formed of regularly spaced aqueous droplets that surround a pair of supporting axial fibers. When a thread is flattened on a microscope slide a small, opaque granule can usually be seen within each droplet. These granules have been thought to be the glycoprotein glue that imparts thread adhesion. Both independent contrast and standard regressions showed that granule size is directly related to droplet volume and indicated that granule volume is about 15% of droplet volume. We attempted to find support for the hypothesized adhesive role of granules by establishing an association between the contact surface area and volume of these granules and the stickiness of the viscous threads of 16 species in the context of a six-variable model that describes thread stickiness. However, we found that granule size made either an insignificant or a small negative contribution to thread stickiness. Consequently, we hypothesize that granules serve to anchor larger, surrounding layers of transparent glycoprotein glue to the axial fibers of the thread, thereby equipping droplets to resist slippage on the axial fibers as these droplets generate adhesion, elongate under a load, and transfer force to the axial fibers.

The Journal of Experimental Biology