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84454075

10.1139/Z85-009

Adaptations of metabolism for freeze tolerance in the gray tree frog, Hyla versicolor

Biochemical adaptations allowing the natural survival of extracellular freezing were examined in the gray tree frog, Hyla versicolor. Laboratory-reared immature adults froze between −1 and −1.5 °C and survived 5 days of freezing at −2 °C as well as repeated rapid bouts of freeze–thaw. Measurements of ice content showed 41.5% of total body water frozen. Glycerol accumulated as the cryoprotectant in sexually mature adult H. versicolor (423 μmol/mL in blood) while both glycerol and glucose accumulated in immature adults (16.3 ± 6.8 and 25.9 ± 11.6 μmol/mL in blood, respectively). Cryoprotectant synthesis was freezing stimulated only and did not occur over long-term cold acclimation at 0 to 1 °C. Cryoprotectant synthesis was correlated with a 203% increase in liver total phosphorylase activity and an increase in phosphorylase a content from 40 to 60%. Activities of 15 other enzymes of intermediary metabolism were determined in liver and leg muscle; activities of most enzymes increased with freezing exposure a...

Canadian Journal of Zoology

85254475

10.1016/J.EJOP.2003.12.001

Ultrastructure and geographic distribution of the genus Paradermamoeba (Gymnamoebia, Thecamoebidae)

The genus Paradermamoeba includes two species with a distinct and unusually thick cell coat. This coat consists of densely packed helical glycostyles, up to 520 nm in length. Perhaps due to the impenetrable properties of the cell coat, we were unable to achieve satisfactory quality of EM fixation in these species until recently. In this study the treatment of cells with dilute Triton X-100 detergent prior to fixation has improved preservation of the ultrastructure of both Paradermamoeba species. Paradermamoeba valamo has an unusual central nucleolus consisting of densely packed fibrils of nucleolar material. A newly isolated strain of P. levis from a UK pond, Priest Pot, forms rounded, single-walled cysts. Both species have enigmatic trichocyst-like bodies in the cytoplasm. Despite the presence of a thick and highly differentiated cell coat, dictyosomes in both species are few and are not more developed than in many other species of gymnamoebae. Neither ultrastructure nor LM morphology indicates the phylogenetic position of Paradermamoeba. It seems that the family Thecamoebidae is a heterogeneous assemblage of unrelated genera. Recent isolation of both P. valamo and P. levis in Switzerland and in the UK indicates the wide distribution of both species in Europe.

European Journal of Protistology

85904441

10.1111/J.1479-8298.2006.00158.X

Structure, mechanism and mechanical properties of pupal attachment in Greta oto (Lepidoptera: Nymphalidae: Ithomiinae)

The structure and mechanism of pupal attachment are described for the nymphalid Greta oto using electron microscopy, and high‐speed and time‐lapse photography. The cremaster is composed of a 3‐D array of hooked setae that engage with silk fibers spun into layers in a pad on the lower leaf surface. Each seta comprises a shaft terminating in a strongly curved hook, tipped with two lateral barbs. These hook into the silk pad, which is densely laid and built‐up in the central portion, flattening out peripherally. Time‐lapse photography showed that silk pad construction by fifth instar larvae is completed in four distinct spinning movements, producing a random fiber arrangement. It is proposed that such a fiber arrangement provides isotropic strength, giving greater flexibility to the attachment. The cremaster is attached to the silk pad by a series of lateral movements of the pupa's posterior abdomen. This movement, together with the shape of the setal hooks, is thought to be integral to the attachment process. Tensile loading tests showed that attachment failure is due to the breakage of the silk pad, which undergoes gradual destruction before releasing the cremaster. The attachment was found to have high tensile strength and fracture toughness, both of which suggest that it has evolved for the dual purpose of preventing the pupa being pulled from the leaf by a predator and preventing the attachment being weakened by wind, which causes the pupa to swing.

Entomological Science

16951300

10.1038/SREP01846

Snake velvet black: Hierarchical micro- and nanostructure enhances dark colouration in Bitis rhinoceros

The West African Gaboon viper (Bitis rhinoceros) is a master of camouflage due to its colouration pattern. Its skin is geometrically patterned and features black spots that purport an exceptional spatial depth due to their velvety surface texture. Our study shades light on micromorphology, optical characteristics and principles behind such a velvet black appearance. We revealed a unique hierarchical pattern of leaf-like microstructures striated with nanoridges on the snake scales that coincides with the distribution of black colouration. Velvet black sites demonstrate four times lower reflectance and higher absorbance than other scales in the UV – near IR spectral range. The combination of surface structures impeding reflectance and absorbing dark pigments, deposited in the skin material, provides reflecting less than 11% of the light reflected by a polytetrafluoroethylene diffuse reflectance standard in any direction. A view-angle independent black structural colour in snakes is reported here for the first time.

Scientific Reports

1676751

10.1073/PNAS.1018202108

Most fertilizing mouse spermatozoa begin their acrosome reaction before contact with the zona pellucida during in vitro fertilization

To fuse with oocytes, spermatozoa of eutherian mammals must pass through extracellular coats, the cumulus cell layer, and the zona pellucida (ZP). It is generally believed that the acrosome reaction (AR) of spermatozoa, essential for zona penetration and fusion with oocytes, is triggered by sperm contact with the zona pellucida. Therefore, in most previous studies of sperm–oocyte interactions in the mouse, the cumulus has been removed before insemination to facilitate the examination of sperm–zona interactions. We used transgenic mouse spermatozoa, which enabled us to detect the onset of the acrosome reaction using fluorescence microscopy. We found that the spermatozoa that began the acrosome reaction before reaching the zona were able to penetrate the zona and fused with the oocyte's plasma membrane. In fact, most fertilizing spermatozoa underwent the acrosome reaction before reaching the zona pellucida of cumulus-enclosed oocytes, at least under the experimental conditions we used. The incidence of in vitro fertilization of cumulus-free oocytes was increased by coincubating oocytes with cumulus cells, suggesting an important role for cumulus cells and their matrix in natural fertilization.

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

34425745

10.1007/BF01632907

Functional anatomy of the valves in the ambulacral system of sea urchins (Echinodermata, Echinoida)

SummaryThe water vascular system of sea urchins is examined with special reference to the valves positioned between the radial vessel and the ampullae of the tube feet. The lips of the valve protrude into the ampulla. Thus the valve functions mainly like a check valve that allows the unidirectional flow of fluid towards the ampulla. Each ampulla-tube foot compartment acts as a semi-autonomous hydraulic system. The lumina of the ampulla and the tube foot are lined with myoepithelia except for the interconnecting channels that pierce the ambulacral plate. The contraction of the ampulla results in an increasing hydraulic pressure that protrudes the tube foot, provided that the valve is closed. The retraction of the tube foot results in a backflow of fluid independent of the condition of the valve. The lips of the valve are folds of the hydrocoel epithelium. The pore slit lies in the midline. The perradial faces of the lips are covered with the squamous epithelium of the lateral water vessel. The ampullar faces are specialized parts of the ampulla myoepithelium. Turgescent cells which form incompressible cushions take the place of the support cells. The valve myocytes run parallel to the pore slit and form processes that run along the base of the ampulla and the perradial channel up to the podial retractor muscle. The findings lead to the hypothesis of multiple control of the ampulla-tube foot system: (1) The mutual activity of the ampulla and the tube foot is indirectly controlled by the lateral and podial nerves which release transmitter substances that diffuse through the connective tissue up to the muscle layers. (2) A muscle-to-muscle conduction causes the simultaneous contraction of the ampulla or the podial retractor muscles. (3) The valve muscles are directly controlled by the processes of the valve myocytes which make contact with the podial retractor. In extreme conditions a backflow of hydrocoel fluid towards the radial water vessel occurs.

Zoomorphology

42276496

10.1126/SCIENCE.1108841

Allometry of Alarm Calls: Black-Capped Chickadees Encode Information About Predator Size

Many animals produce alarm signals when they detect a potential predator, but we still know little about the information contained in these signals. Using presentations of 15 species of live predators, we show that acoustic features of the mobbing calls of black-capped chickadees (Poecile atricapilla) vary with the size of the predator. Companion playback experiments revealed that chickadees detect this information and that the intensity of mobbing behavior is related to the size and threat of the potential predator. This study demonstrates an unsuspected level of complexity and sophistication in avian alarm calls.

Science

53496043

10.1016/J.COSSMS.2004.01.005

Bioinspired synthesis of mesoporous silicas

Abstract Recent years have witnessed rapid growth in the number of new investigations at the interface of materials chemistry and biology. This review highlights the recent developments in the studies of protein-mediated silica biomineralization in diatoms and the “downscaling” and “upscaling” models derived thereof, as well as the recent progress in the fabrication of artificial silicas with novel pore structures and morphologies at different length scales based on these new insights into biosilica formation.

Current Opinion in Solid State & Materials Science

32133351

10.1126/SCIENCE.290.5497.1744

Formation of sphalerite (ZnS) deposits in natural biofilms of sulfate-reducing bacteria.

Abundant, micrometer-scale, spherical aggregates of 2- to 5-nanometer-diameter sphalerite (ZnS) particles formed within natural biofilms dominated by relatively aerotolerant sulfate-reducing bacteria of the family Desulfobacteriaceae. The biofilm zinc concentration is about 10(6) times that of associated groundwater (0.09 to 1.1 parts per million zinc). Sphalerite also concentrates arsenic (0.01 weight %) and selenium (0.004 weight %). The almost monomineralic product results from buffering of sulfide concentrations at low values by sphalerite precipitation. These results show how microbes control metal concentrations in groundwater- and wetland-based remediation systems and suggest biological routes for formation of some low-temperature ZnS deposits.

Science

86888547

10.2307/1442721

Skin and Aestivational Cocoon of the Aquatic Amphibian, Siren intermedia Le Conte

The skin of Siren intermedia is fully metamorphosed, amphibian-like, and specialized in its cocoon-producing function. During aestivation in burrows in the bottoms of dry ponds, epidermal and dermal skin glands secrete a cocoon which covers the entire body except the mouth. This structure, remarkably like the cocoons of African lungfishes, retards desiccation and permits sirens to remain in periodically dry, aquatic environments. This adaptive strategy may be alternative to that of avoiding drought by overland movement to nearby water.

Copeia

5996231

10.1093/ICB/ICQ122

Mechanics without muscle: biomechanical inspiration from the plant world.

Plant and animal biomechanists have much in common. Although their frame of reference differs, they think about the natural world in similar ways. While researchers studying animals might explore airflow around flapping wings, the actuation of muscles in arms and legs, or the material properties of spider silk, researchers studying plants might explore the flow of water around fluttering seaweeds, the grasping ability of climbing vines, or the material properties of wood. Here we summarize recent studies of plant biomechanics highlighting several current research themes in the field: expulsion of high-speed reproductive projectiles, generation of slow movements by shrinking and swelling cell walls, effects of ontogenetic shifts in mechanical properties of stems, flexible reconfiguration and material properties of seaweeds under crashing waves, and the development of botanically-inspired commercial products. Our hope is that this synopsis will resonate with both plant and animal biologists, encourage cross-pollination across disciplines, and promote fruitful interdisciplinary collaborations in the future.

Integrative and Comparative Biology

205496332

10.1038/NRMICRO1442

Bug juice: harvesting electricity with microorganisms

It is well established that some reduced fermentation products or microbially reduced artificial mediators can abiotically react with electrodes to yield a small electrical current. This type of metabolism does not typically result in an efficient conversion of organic compounds to electricity because only some metabolic end products will react with electrodes, and the microorganisms only incompletely oxidize their organic fuels. A new form of microbial respiration has recently been discovered in which microorganisms conserve energy to support growth by oxidizing organic compounds to carbon dioxide with direct quantitative electron transfer to electrodes. These organisms, termed electricigens, offer the possibility of efficiently converting organic compounds into electricity in self-sustaining systems with long-term stability.

Nature Reviews Microbiology

6867657

10.1073/PNAS.1018259108

Intracellular invasion of green algae in a salamander host

The association between embryos of the spotted salamander (Ambystoma maculatum) and green algae (“Oophila amblystomatis” Lamber ex Printz) has been considered an ectosymbiotic mutualism. We show here, however, that this symbiosis is more intimate than previously reported. A combination of imaging and algal 18S rDNA amplification reveals algal invasion of embryonic salamander tissues and cells during development. Algal cells are detectable from embryonic and larval Stages 26–44 through chlorophyll autofluorescence and algal 18S rDNA amplification. Algal cell ultrastructure indicates both degradation and putative encystment during the process of tissue and cellular invasion. Fewer algal cells were detected in later-stage larvae through FISH, suggesting that the decline in autofluorescent cells is primarily due to algal cell death within the host. However, early embryonic egg capsules also contained encysted algal cells on the inner capsule wall, and algal 18S rDNA was amplified from adult reproductive tracts, consistent with oviductal transmission of algae from one salamander generation to the next. The invasion of algae into salamander host tissues and cells represents a unique association between a vertebrate and a eukaryotic alga, with implications for research into cell–cell recognition, possible exchange of metabolites or DNA, and potential congruence between host and symbiont population structures.

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

3019375

10.1038/NCOMMS13835

Carbon storage in US wetlands

Wetland soils contain some of the highest stores of soil carbon in the biosphere. However, there is little understanding of the quantity and distribution of carbon stored in our remaining wetlands or of the potential effects of human disturbance on these stocks. Here we use field data from the 2011 National Wetland Condition Assessment to provide unbiased estimates of soil carbon stocks for wetlands at regional and national scales. We find that wetlands in the conterminous United States store a total of 11.52 PgC, much of which is within soils deeper than 30 cm. Freshwater inland wetlands, in part due to their substantial areal extent, hold nearly ten-fold more carbon than tidal saltwater sites—indicating their importance in regional carbon storage. Our data suggest a possible relationship between carbon stocks and anthropogenic disturbance. These data highlight the need to protect wetlands to mitigate the risk of avoidable contributions to climate change.

Nature Communications

427175

10.1111/J.1469-7580.2007.00762.X

Muscle moment arms of pelvic limb muscles of the ostrich (Struthio camelus)

Muscle moment arms were measured for major muscles of the pelvic limb of the ostrich (Struthio camelus) in order to assess specific functional behaviour and to apply this to locomotor performance. Pelvic limbs of six juvenile ostriches were used for this study. The tendon travel technique was used to measure moment arms of 21 muscles at the hip, knee, ankle and metatarsophalangeal joints throughout the ranges of motion observed during level running. Six of the 21 muscles measured were found to have moment arms that did not change with joint angle, whilst the remainder all demonstrated angle‐dependent changes for at least one of the joints crossed. Moment arm lengths tended to be longest for the large proximal muscles, whilst the largest relative changes were found for the moment arms of the distal muscles. For muscles where moment arm varied with joint angle: all hip muscles were found to have increasing moment arms with extension of the joint, knee flexors were found to have moment arms that increased with extension, knee extensor moment arms were found to increase with flexion and ankle extensor moment arms increased with extension. The greatest relative changes were observed in the flexors of the metatarsophalangeal joint, for which a three‐fold increase in moment arm was observed from flexion to full extension. Changes in muscle moment arm through the range of motion studied appear to optimize muscle function during stance phase, increasing the effective mechanical advantage of these muscles.

Journal of Anatomy

135630505

10.1016/S0928-4931(00)00133-8

Biomimetic structure design — a possible approach to change the brittleness of ceramics in nature☆

Based on the analysis on structure of natural biomaterials, two kinds of ceramic composites with high toughness have been designed and prepared: one is fibrous monolithic Si3N4/BN composite imitating bamboos or trees in structure, the other is laminated Si3N4/BN composite imitating nacre in structure. Plastic forming methods, including extrusion and roll compaction, respectively, followed by hot-pressed sintering are used to prepare these two materials with particular structures. Both of the two composites have high values of fracture toughness and work of fracture: fracture toughness are 24 MPa m1/2 and 28 MPa m1/2, respectively, for fibrous monolithic and laminated Si3N4/BN composites, and works of fracture are both more than 4000 J/m2. The load-displacement curves reveal that these two materials with biomimetic structure exhibit non-brittle feature when applied load to fracture. Through analysis on fractographs of the materials, it is revealed that high toughness comes from the synergistic toughening among multi-level toughening mechanisms in different scales: weak interfaces, whiskers and elongated grains toughening in ceramic matrix cells.

Materials Science and Engineering: C

6875924

10.1038/SREP02108

Spiderweb deformation induced by electrostatically charged insects

Capture success of spider webs has been associated with their microstructure, ornamentation, and wind-induced vibrations. Indirect evidence suggests that statically charged objects can attract silk thread, but web deformations induced by charged insects have not yet been described. Here, we show under laboratory conditions that electrostatically charged honeybees, green bottle flies, fruit flies, aphids, and also water drops falling near webs of cross-spiders (Araneus diadematus) induce rapid thread deformation that enhances the likelihood of physical contact, and thus of prey capture.

Scientific Reports

11051531

10.3354/AME047275

Comparison of surface microfouling and bacterial attachment on the egg capsules of two molluscan species representing Cephalopoda and Neogastropoda

Many organisms naturally defend themselves against microbial attachment and biofoul- ing in the marine environment. In this study, we investigated microbial fouling on 2 molluscan egg capsules using scanning electron microscopy (SEM), two-photon laser scanning microscopy (TPLSM) with bacterial viability staining and bacterial attachment experiments with the biofilm-forming Pseudoalteromonas sp. S91 in flow chambers. Results indicated that early stage egg capsules of Dicathais orbita (Neogastropoda) are relatively free of surface microorganisms. Egg capsules during the trocophore stage had a regularly ridged microtexture, but as capsules matured, shedding of the outer wall was observed, followed by the extrusion of unidentified droplets, which then accumulated on the capsule surface in association with bacteria. By comparison, the egg capsules of Sepioteuthis australis (Cephalopoda) were found to have an irregular surface with many hills and valleys that accommodate colonization by a variety of microorganisms. At the later stages of development these squid egg capsules become heavily colonized by algal spores. Cross sections of egg capsules revealed that S. australis capsule walls were about 12 times thicker than D. orbita egg capsules. Staining the egg capsules with BacLight™ also revealed a significantly thicker biofilm, with more live and dead bacteria on S. australis capsules than on those of D. orbita (p < 0.05). Flow chamber exper- iments indicated that the surface of S. australis capsules provided a suitable substrate for colonization by Pseudoalteromonas sp. S91, whereas colonization was significantly less on D. orbita egg capsules after 24 and 72 h (p < 0.01). These experiments indicated that D. orbita egg capsules are better defended against fouling microbes than are the eggs of S. australis. D. orbita appears to use a combi- nation of physical, mechanical and possibly chemical defense mechanisms to reduce fouling on their egg capsules.

Aquatic Microbial Ecology

4305912

10.1038/35018159

Insect metabolism: Preventing cyanide release from leaves

Organisms that produce hydrogen cyanide gas to protect themselves against predators can do so by the enzymatic breakdown of a class of compounds known as cyanogens (such as cyanogenic glycosides). Here we show how a neotropical butterfly, Heliconius sara, can avoid the harmful effects of the cyanogenic leaves of Passiflora auriculata (passion vine), on which its larvae feed exclusively. To our knowledge this is the first example of an insect that is able to metabolize cyanogens and thereby prevent the release of cyanide. The mechanistic details of this pathway might suggest new ways to make cyanogenic crops more useful as a food source.

Nature

55168063

10.1163/000579511X570893

Underwater components of humpback whale bubble-net feeding behaviour

Summary Humpback whales (Megaptera novaeangliae) employ a unique and complex foraging behaviour — bubble-netting — that involves expelling air underwater to form a vertical cylinder-ring of bubbles around prey. We used digital suction cup tags (DTAGs) that concurrently measure pitch, roll, heading, depth and sound (96 kHz sampling rate), to provide the first depiction of the underwater behaviours in which humpback whales engage during bubble-net feeding. Body mechanics and swim paths were analysed using custom visualization software that animates the underwater track of the whale and quantifies tag sensor values. Bubble production was identified aurally and through spectrographic analysis of tag audio records. We identified two classes of behaviour (upward-spiral; 6 animals, 118 events and double-loop; 3 animals, 182 events) that whales used to create bubble nets. Specifically, we show the actual swim path of the whales (e.g., number of revolutions, turning rate, depth interval of spiral), when and where in the process bubbles were expelled and the pattern of bubble expulsion used by the animals. Relative to other baleanopterids, bubble-netting humpbacks demonstrate increased manoeuvrability probably aided by a unique hydrodynamicly enhanced body form. We identified an approximately 20 m depth or depth interval limit to the use of bubble nets and suggest that this limit is due to the physics of bubble dispersal to which humpback whales have behaviourally adapted. All animals were feeding with at

Behaviour

15324994

10.1016/J.ANBEHAV.2014.07.008

Collective decision making and social interaction rules in mixed-species flocks of songbirds

Associations in mixed-species foraging groups are common in animals, yet have rarely been explored in the context of collective behaviour. Despite many investigations into the social and ecological conditions under which individuals should form groups, we still know little about the specific behavioural rules that individuals adopt in these contexts, or whether these can be generalized to heterospecifics. Here, we studied collective behaviour in flocks in a community of five species of woodland passerine birds. We adopted an automated data collection protocol, involving visits by RFID-tagged birds to feeding stations equipped with antennae, over two winters, recording 91 576 feeding events by 1904 individuals. We demonstrated highly synchronized feeding behaviour within patches, with birds moving towards areas of the patch with the largest proportion of the flock. Using a model of collective decision making, we then explored the underlying decision rule birds may be using when foraging in mixed-species flocks. The model tested whether birds used a different decision rule for conspecifics and heterospecifics, and whether the rules used by individuals of different species varied. We found that species differed in their response to the distribution of conspecifics and heterospecifics across foraging patches. However, simulating decisions using the different rules, which reproduced our data well, suggested that the outcome of using different decision rules by each species resulted in qualitatively similar overall patterns of movement. It is possible that the decision rules each species uses may be adjusted to variation in mean species abundance in order for individuals to maintain the same overall flock-level response. This is likely to be important for maintaining coordinated behaviour across species, and to result in quick and adaptive flock responses to food resources that are patchily distributed in space and time.

Animal Behaviour

86727774

10.1086/680231

A Passionate Free Climber: Structural Development and Functional Morphology of the Adhesive Tendrils in Passiflora discophora

Premise of research. Passiflora discophora is exceptional among passion flowers for its climbing strategy, using branched tendrils with terminal adhesive pads instead of coiling tendrils as typical within this family. This article investigates the structural development and morphology of these adhesive pads and aims to understand the underlying structure-function relationship of the attachment process. Based on our results, we discuss possible mechanical consequences of the tendril structure and compare our findings with similar attachment systems in unrelated species in order to identify general strategies of this mode of attachment. Methodology. We investigated the temporal development of the attachment process, including detailed studies of the morphology and anatomy of the adhesive pads, using LM with different staining procedures and SEM. Pivotal results. Young tendrils establish initial contact with a supporting substrate by interlocking with their hook-shaped tips. Touch stimuli induce the tips to develop into adhesive pads by callus-like growth of papillate epidermal cells. Fully grown pads are hemispherical on flat substrates or completely fill out larger cavities of the substrate. By apical cell division, the pad tissue perfectly mimics the microtopography of the substrate and also grows into minute gaps and fissures, establishing firm anchorage by optimal form closure. Additionally, an extracellular substance is visible at the interface between pad and substrate surface, which might act as adhesive. Conclusions. The opportunistic growth and cellular structure make the tendrils and adhesive pads of P. discophora a highly adaptive attachment system. Comparison with other not closely related taxa reveals general principles of this climbing mode, namely, (1) branched tendrils with multiple adhesive pads, (2) papillate cells establishing optimal form closure with the substrate and in some species additionally secreting adhesive substances, (3) free coiling of axes, and (4) persisting anchorage after senescence.

International Journal of Plant Sciences

88194727

10.2307/2388496

Microenvironmental Role of a Secreted Aqueous Solution in the Afro-Alpine Plant Lobelia keniensis

On montre que la solution aqueuse et mucilagineuse secretee par L. kiniensis sert a preserver du froid les bourgeons vegetatifs. La substance mucilagineuse identifiee a la pectine servirait a proteger la reserve d'eau de l'evaporation

Biotropica

35900884

10.1111/J.1462-2920.2007.01301.X

Life on the rocks.

Biofilms are interface micro-habitats formed by microbes that differ markedly from those of the ambient environment. The term 'subaerial biofilm' (SAB) was coined for microbial communities that develop on solid mineral surfaces exposed to the atmosphere. Subaerial biofilms are ubiquitous, self-sufficient, miniature microbial ecosystems that are found on buildings, bare rocks in deserts, mountains, and at all latitudes where direct contact with the atmosphere and solar radiation occurs. Subaerial biofilms on exposed terrestrial surfaces are characterized by patchy growth that is dominated by associations of fungi, algae, cyanobacteria and heterotrophic bacteria. Inherent subaerial settlers include specialized actinobacteria (e.g. Geodermatophilus), cyanobacteria and microcolonial fungi. Individuals within SAB communities avoid sexual reproduction, but cooperate extensively with one another especially to avoid loss of energy and nutrients. Subaerial biofilm metabolic activity centres on retention of water, protecting the cells from fluctuating environmental conditions and solar radiation as well as prolonging their vegetative life. Atmospheric aerosols, gases and propagatory particles serve as sources of nutrients and inoculum for these open communities. Subaerial biofilms induce chemical and physical changes to rock materials, and they penetrate the mineral substrate contributing to rock and mineral decay, which manifests itself as bio-weathering of rock surfaces. Given their characteristic slow and sensitive growth, SAB may also serve as bioindicators of atmospheric and/or climate change.

Environmental Microbiology

209474787

10.1016/J.JCIS.2019.12.082

The position of lysine controls the catechol-mediated surface adhesion and cohesion in underwater mussel adhesion.

Intensive studies have found that 3,4-dihydroxyphenylalanine (Dopa) is one of the key molecules for underwater mussel adhesion. Although basic mechanisms of mussel adhesion have been elucidated, little is known about how mussels control the balance between surface adhesion and cohesion, which is critical for successful adhesion without peeling and/or tearing. In this work, we focused on lysine (Lys) molecules which are frequently flanked to Dopa residues in interfacial adhesive proteins, specifically their synergy and anti-synergy on surface adhesion and cohesion. Three model peptides were designed to characterize flanking Lys effects. Through nano-mechanistic analyses, we found that flanking Lys enhanced surface adhesion but disrupted Fe3+-mediated cohesion. Through nuclear magnetic resonance analyses and density functional theory calculations, we corroborated the synergetic effect on surface adhesion and anti-synergetic effect on cohesion. We also confirmed the consistency of flanking Lys effects in the actual protein system. Thus, we, for the first time, discovered that each Dopa molecule in interfacial adhesive proteins is participated in surface adhesion and cohesion differently through controlling the existence of flanking Lys. Our discovery enlightens how nature designs adhesive proteins through according roles of Dopa.

Joint International Conference on Information Sciences

119835522

10.1126/SCIENCE.318.5852.904

Seeking Nature's Inner Compass

AUCKLAND, NEW ZEALAND-- Michael Walker has navigated cultures and courted controversy in his quest to prove that life forms possess a single organ for perceiving magnetic fields: a sensor based on magnetite.

Science

16643149

10.1029/2006PA001395

Reversed deep-sea carbonate ion basin gradient during Paleocene-Eocene thermal maximum

[1] The Paleocene-Eocene thermal maximum (PETM, ∼55 Ma ago) was marked by widespread CaCO3 dissolution in deep-sea sediments, a process that has been attributed to massive release of carbon into the ocean-atmosphere system. The pattern of carbonate dissolution is key to reconstructing changes in deep sea carbonate chemistry and, ultimately, the rate, magnitude, and location of carbon input. Here we show that during the PETM, the deep-sea undersaturation was not homogeneous among the different ocean basins. Application of a sediment model to a suite of data records from different sites and ocean basins shows that a globally uniform decrease in deep-sea carbonate ion concentration ([CO32−]) is inconsistent with the data. Rather, we demonstrate that deep-sea [CO32−] increased from the Atlantic through the Southern Ocean into the Pacific. Our results show that the PETM deep-sea [CO32−] basin gradient during dissolution was reversed relative to the modern.

Paleoceanography

84688191

10.2307/1379954

Pinna Temperature in Exercising Jackrabbits, Lepus californicus

Pinna surface temperatures of Lepus californicus were examined radiographically before and after forced exercise (e.g., running at about 6 km/h for 6 min) in an outdoor enclosure. Air temperatures were from −1.6 to +19.4°C, and radiant sky temperatures were from —27 to +22°C. In resting animals, average pinna surface temperature was only 0.3 to 2.5°C above air temperature, and pinna arteries were not evident radiographically. Immediately after exercise, average pinna temperature was often near 30°C and pinna arteries were evident, indicating vasodilation. Cooling of the pinnae to resting temperatures after exercise generally took 15 to 25 min. Calculations indicate that the pinnae can dissipate most of the excess metabolic heat generated during the exercise examined, and it is suggested that the role of the pinnae as dissipators of exercise-induced heat loads should be considered as a factor in the evolution of pinna size.

Journal of Mammalogy

9048248

10.2307/1543624

Propagation and Perception of Bioluminescence: Factors Affecting Counterillumination as a Cryptic Strategy

Many deep-sea species, particularly crustaceans, cephalopods, and fish, use photophores to illuminate their ventral surfaces and thus disguise their silhouettes from predators viewing them from below. This strategy has several potential limitations, two of which are examined here. First, a predator with acute vision may be able to detect the individual photophores on the ventral surface. Second, a predator may be able to detect any mismatch between the spectrum of the bioluminescence and that of the background light. The first limitation was examined by modeling the perceived images of the counterillumination of the squid Abralia veranyi and the myctophid fish Ceratoscopelus maderensis as a function of the distance and visual acuity of the viewer. The second limitation was addressed by measuring downwelling irradiance under moonlight and starlight and then modeling underwater spectra. Four water types were examined: coastal water at a depth of 5 m and oceanic water at 5, 210, and 800 m. The appearance of the counterillumination was more affected by the visual acuity of the viewer than by the clarity of the water, even at relatively large distances. Species with high visual acuity (0.11° resolution) were able to distinguish the individual photophores of some counterilluminating signals at distances of several meters, thus breaking the camouflage. Depth and the presence or absence of moonlight strongly affected the spectrum of the background light, particularly near the surface. The increased variability near the surface was partially offset by the higher contrast attenuation at shallow depths, which reduced the sighting distance of mismatches. This research has implications for the study of spatial resolution, contrast sensitivity, and color discrimination in deep-sea visual systems.

The Biological Bulletin

56041483

10.1080/03605309508821153

On Nonexistence of any λ0-invariand positive harmonic function, a counter example to stroock' conjecture

Consider a sub-Markovian semigroup such that λ0, the border number between recrrence and transience, equals zero. In 1982, D. W. Stroock conjectured that under general hypotheses on the semi-group the corresponding process always admits an invariant measure. In this paper we present an example of a second order elliptic operator P with a generalized principal eigenvalue λ0 which equals zero such that the parabolic equation does not admit any positive invariant P—harmonic function and also any invariant measure. This gives a counter example to Stroock's conjecture for diffusion processes. We also present an example of a complete Riemannian manifold M which does not admit any positive invariant harmonic function while λ0, the bottom of the spectrum of M, is zero. This gives a partial answer to a question of Stroock and Sullivan.

Communications in Partial Differential Equations

14543035

10.1242/JEB.123893

Remora fish suction pad attachment is enhanced by spinule friction

ABSTRACT The remora fishes are capable of adhering to a wide variety of natural and artificial marine substrates using a dorsal suction pad. The pad is made of serial parallel pectinated lamellae, which are homologous to the dorsal fin elements of other fishes. Small tooth-like projections of mineralized tissue from the dorsal pad lamella, known as spinules, are thought to increase the remora's resistance to slippage and thereby enhance friction to maintain attachment to a moving host. In this work, the geometry of the spinules and host topology as determined by micro-computed tomography and confocal microscope data, respectively, are combined in a friction model to estimate the spinule contribution to shear resistance. Model results are validated with natural and artificially created spinules and compared with previous remora pull-off experiments. It was found that spinule geometry plays an essential role in friction enhancement, especially at short spatial wavelengths in the host surface, and that spinule tip geometry is not correlated with lamellar position. Furthermore, comparisons with pull-off experiments suggest that spinules are primarily responsible for friction enhancement on rough host topologies such as shark skin. Summary: The geometry of remora fish suction disc spinules increases passive friction on rough host surfaces such as shark skin.

The Journal of Experimental Biology

3660431

10.1093/AOBPLA/PLV050

Inter-plant communication through mycorrhizal networks mediates complex adaptive behaviour in plant communities

Trees can communicate with each other through networks in soil. Much like social networks or neural networks, the fungal mycelia of mycorrhizas allow signals to be sent between trees in a forest. These mycorrhizal networks are effectively an information highway, with recent studies demonstrating the exchange of nutritional resources, defence signals and allelochemicals. Sensing and responding to networked signals elicits complex behavioural responses in plants. This ability to communicate ('tree talk') is a foundational process in forest ecosystems.

Aob Plants

27810681

10.1073/PNAS.0709246105

Assembly mechanism of recombinant spider silk proteins

Spider silk threads are formed by the irreversible aggregation of silk proteins in a spinning duct with dimensions of only a few micrometers. Here, we present a microfluidic device in which engineered and recombinantly produced spider dragline silk proteins eADF3 (engineered Araneus diadematus fibroin) and eADF4 are assembled into fibers. Our approach allows the direct observation and identification of the essential parameters of dragline silk assembly. Changes in ionic conditions and pH result in aggregation of the two proteins. Assembly of eADF3 fibers was induced only in the presence of an elongational flow component. Strikingly, eADF4 formed fibers only in combination with eADF3. On the basis of these results, we propose a model for dragline silk aggregation and early steps of fiber assembly in the microscopic regime.

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

33323731

10.1007/BF00300577

The role of kinship in helping decisions among white-fronted bee-eaters

SummaryWhite-fronted bee-eaters (Merops bullockoides) are cooperative breeders in which half of all nesting attempts are assisted by non-breeding adults in addition to the breeding pair. These “helpers” assist in all aspects of nesting and their aid significantly increases fledging success. The social unit in these bee-eaters is an extended family clan in which multiple pairs may breed simultaneously (plural breeding). As a result, helpers often have to choose how to allocate their aid among several potential recipients to whom they are unequally related. Using five years of data from a color-marked and genealogically known population of white-fronted bee-eaters in Kenya, we examined the role of kinship in three helping “decisions”: 1) whether or not to become a helper, 2) whom to help, and 3) how much help to provide.1)Kinship between potential donor and recipient was a significant predictor of the likelihood of helping. Fully 44% of the individuals that could have become helpers did not do so. Many of these non-helpers were unrelated mates (“in-laws”) that had paired into their partner's clan and had no genetic link to the available recipients. Others were natal clan members with only distant genealogical ties to the breeders. The conditional probability of helping (see text for definition) decreased significantly with decreasing rh(coefficient of relatedness) between the potential helper and nestling recipients. The presumed cost of helping was a second significant predictor of whether or not a bird became a helper. We considered the expending of effort in providing aid and the delaying of personal reproduction to be costs of helping. Potential helpers that had engaged in high effort activities in the few weeks prior to the helping opportunity showed a decreased likelihood of becoming helpers. Similarly, paired birds (which by virtue of having a mating partner had a greater potential of breeding) were less likely to become helpers than were single individuals.2)Bee-eater helpers preferentially chose to aid their closest genetic relatives. The average relatedness between helpers and the nestlings receiving their aid was 0.33. This degree of kinship was significantly greater than that expected if helpers had selected recipient nests randomly from among those available within their clans. Further evidence of kin discrimination came from analysis of 115 instances in which a helper had two or more nests of differing relatedness simultaneously available as potential recipients. In 108 cases (94%), the helper aided the most closely related one.3)The magnitude of the helping contribution (as measured by provisioning rate) showed no pattern with relatedness between donor and recipient. These data allow testing of various theoretical models for the allocation of aid among kin. Since bee-eaters helped at only one nest at a time, and selected the nest with the most closely related young available, their behavior conforms to an allor-none case of a diminishing returns model and is inconsistent with alternative models based upon the distribution of aid in proportion to relatedness. We conclude that kinship is a major determinant in the decisions both of whether to become a helper, and of whom to help, in white-fronted bee-eaters.

Behavioral Ecology and Sociobiology

294987

10.1126/SCIENCE.1060281

Nitrogen Fixation by Symbiotic and Free-Living Spirochetes

Spirochetes from termite hindguts and freshwater sediments possessed homologs of a nitrogenase gene (nifH) and exhibited nitrogenase activity, a previously unrecognized metabolic capability in spirochetes. Fixation of 15-dinitrogen was demonstrated with termite gut Treponema ZAS-9 and free-livingSpirochaeta aurantia. Homologs of nifH were also present in human oral and bovine ruminal treponemes. Results implicate spirochetes in the nitrogen nutrition of termites, whose food is typically low in nitrogen, and in global nitrogen cycling. These results also proffer spirochetes as a likely origin of certainnifHs observed in termite guts and other environments that were not previously attributable to known microbes.

Science

73419287

10.1016/J.CUB.2019.01.026

The Long and Short of Hearing in the Mosquito Aedes aegypti

Mating behavior in Aedes aegypti mosquitoes occurs mid-air and involves the exchange of auditory signals at close range (millimeters to centimeters) [1-6]. It is widely assumed that this intimate signaling distance reflects short-range auditory sensitivity of their antennal hearing organs to faint flight tones [7, 8]. To the contrary, we show here that male mosquitoes can hear the female's flight tone at surprisingly long distances-from several meters to up to 10 m-and that unrestrained, resting Ae. aegypti males leap off their perches and take flight when they hear female flight tones. Moreover, auditory sensitivity tests of Ae. aegypti's hearing organ, made from neurophysiological recordings of the auditory nerve in response to pure-tone stimuli played from a loudspeaker, support the behavioral experiments. This demonstration of long-range hearing in mosquitoes overturns the common assumption that the thread-like antennal hearing organs of tiny insects are strictly close-range ears. The effective range of a hearing organ depends ultimately on its sensitivity [9-13]. Here, a mosquito's antennal ear is shown to be sensitive to sound levels down to 31 dB sound pressure level (SPL), translating to air particle velocity at nanometer dimensions. We note that the peak of energy of the first formant of the vowels of the human speech spectrum range from about 200-1,000 Hz and is typically spoken at 45-70 dB SPL; together, they lie in the sweet spot of mosquito hearing. VIDEO ABSTRACT.

Current Biology

53060421

10.1002/GRL.50710

Landscape‐scale carbon storage associated with beaver dams

[1] Beaver meadows form when beaver dams promote prolonged overbank flooding and floodplain retention of sediment and organic matter. Extensive beaver meadows form in broad, low-gradient valley segments upstream from glacial terminal moraines. Surveyed sediment volume and total organic carbon content in beaver meadows on the eastern side of Rocky Mountain National Park are extrapolated to create a first-order approximation of landscape-scale carbon storage in these meadows relative to adjacent uplands. Differences in total organic carbon between abandoned and active beaver meadows suggest that valley-bottom carbon storage has declined substantially as beaver have disappeared and meadows have dried. Relict beaver meadows represent ~8% of total carbon storage within the landscape, but the value was closer to 23% when beaver actively maintained wet meadows. These changes reflect the general magnitude of cumulative effects in heterotrophic respiration and organic matter oxidation associated with historical declines in beaver populations across the continent.

Geophysical Research Letters

36131978

10.1098/RSIF.2007.1338

Oxygen mass transfer in a model three-dimensional artery

Arterial geometry is commonly non-planar and associated with swirling blood flow. In this study, we examine the effect of arterial three-dimensionality on the distribution of wall shear stress (WSS) and the mass transfer of oxygen from the blood to the vessel wall in a U-bend, by modelling the blood vessels as either cylindrical or helical conduits. The results show that under physiological flow conditions, three-dimensionality can reduce both the range and extent of low WSS regions and substantially increase oxygen flux through the walls. The Sherwood number and WSS distributions between the three-dimensional helical model and a human coronary artery show remarkable qualitative agreement, implying that coronary arteries may potentially be described with a relatively simple idealized three-dimensional model, characterized by a small number of well-defined geometric parameters. The flow pattern downstream of a planar bend results in separation of the Sh number and WSS effects, a finding that implies means of investigating them individually.

Journal of the Royal Society Interface

17072933

10.1364/OE.21.000764

Improved light extraction in the bioluminescent lantern of a Photuris firefly (Lampyridae).

A common problem of light sources emitting from an homogeneous high-refractive index medium into air is the loss of photons by total internal reflection. Bioluminescent organisms, as well as artificial devices, have to face this problem. It is expected that life, with its mechanisms for evolution, would have selected appropriate optical structures to get around this problem, at least partially. The morphology of the lantern of a specific firefly in the genus Photuris has been examined. The optical properties of the different parts of this lantern have been modelled, in order to determine their positive or adverse effect with regard to the global light extraction. We conclude that the most efficient pieces of the lantern structure are the misfit of the external scales (which produce abrupt roughness in air) and the lowering of the refractive index at the level of the cluster of photocytes, where the bioluminescent production takes place.

arXiv: Optics

3036770

10.1007/S00468-010-0417-X

Salt tolerance mechanisms in mangroves: a review

Mangroves are woody plants which form the dominant vegetation in tidal, saline wetlands along tropical and subtropical coasts. The current knowledge concerning the most striking feature of mangroves i.e., their unique ability to tolerate high salinity is summarized in the present review. In this review, we shall discuss recent studies that have focused on morphological, anatomical, physiological, biochemical, molecular and genetic attributes associated with the response to salinity, some of which presumably function to mediate salt tolerance in the mangroves. Here we shall also review the major advances recently made at both the genetic and the genomic levels in mangroves. Salinity tolerance in mangroves depends on a range of adaptations, including ion compartmentation, osmoregulation, selective transport and uptake of ions, maintenance of a balance between the supply of ions to the shoot, and capacity to accommodate the salt influx. The tolerance of mangroves to a high saline environment is also tightly linked to the regulation of gene expression. By integrating the information from mangroves and performing comparisons among species of mangroves and non-mangroves, we could give a general picture of salt tolerance mechanisms of mangroves, thus providing a new avenue for development of salt tolerance in crop plants through effective breeding strategies and genetic engineering techniques.

Trees-structure and Function

12289765

10.1007/S00425-010-1270-2

Desiccation resistance of adhesive secretion in the protocarnivorous plant Roridula gorgonias as an adaptation to periodically dry environment

To analyse the change of mass in the resinous secretion of Roridula gorgonias, we carried out long-term measurements using a computerised ultra microbalance. In contrast to the aqueous mucilage of other carnivorous flypaper traps, this water-insoluble secretion does not desiccate even in dead and formalin-preserved plants. We found no significant desiccation of secretory drops within 10 h of continuous weighing. After 100 days of the secretion exposure to dry conditions, only about 8% of the mass was lost. Interestingly, returning these samples to humid conditions resulted in a mass recovery to the initial amount. This property of the secretion is discussed as an ecological adaptation to the periodically dry Fynbos habitat of the plant.

Planta

84922230

10.1016/0022-1910(73)90064-4

Physiological colour change in the elytra of the hercules beetle, Dynastes hercules

Abstract The male of the hercules beetle, Dynastes hercules, is able to change the colour of its elytra from yellowish to black and back again to yellowish within a few minutes. The epicuticle of the elytra is transparent and about 3 μm thick. Below it is a yellow spongy layer that is usually about 5 μm thick. The cuticle below the yellow sponge is black. When the layer of yellow sponge is air filled it becomes optically heterogeneous, and the light reflected from the elytra is yellow. When the yellow sponge is liquid filled it becomes optically homogeneous, and the black cuticle below is seen. If a beetle that has yellowish elytra is placed in a saturated atmosphere, the elytra become black. When the relative humidity is appreciably reduced, yellow patches begin to appear on the elytra, usually within 30 sec to 2 min. However, if the beetle is kept at a constant relative humidity that previously caused yellowing, it will become black given enough time. Most colour changes observed were clearly in response to changes in the ambient humidity and were not affected when the beetles were kept in the light or in total darkness nor by blackening their eyes or prodding them or exposing them to sounds of different intensities or frequencies. If an elytron is removed from a live beetle, it changes colour in response to changes in relative humidity exactly like the elytron left attached. When a restricted area of the elytra is subjected to a humidity that normally causes blackening and an adjacent area to a humidity that normally causes yellowing, both change colour in the expected way. This local control of colour change seems to preclude hormonal control. It is suggested that the epidermal cells or both the epidermal and blood cells in the elytra are responsible for the hydration and dehydration of the layer of yellow sponge.

Journal of Insect Physiology

73701054

10.1016/J.SAJB.2013.03.018

Photosynthetic adaptation of two semi-arid species of Gethyllis (Kukumakranka) to drought-and-shade stress

Abstract Gethyllis multifolia and Gethyllis villosa are winter-growing, summer-blooming, deciduous and bulbous geophytes that grow naturally in the semi-arid ‘Succulent Karoo Biome’ of South Africa. G. multifolia is threatened in its natural habitat and resides in the ‘Vulnerable’ category of the ‘Red Data List of Southern African Plants’. Previous investigations suggested that G. multifolia is more sensitive to drought stress than G. villosa and that both species adopted certain morphological changes in their leaves during shade stress. Current models indicate that this biome is being exposed to increasingly drier conditions and shading from encroaching indigenous plant species. In this study, the photosynthetic gas exchange responses of both species to drought and shade stresses were investigated and the ‘Vulnerable’ conservation status of G. multifolia. This investigation found that during drought stress G. villosa had a more enhanced photosynthetic performance than G. multifolia which appears not to be related to foliar adaptations such as specific leaf mass (SLM), but to the G. villosa's leaves maintaining their stomatal conductance (Gs), photosynthetic light compensation (LCP) and photon yields. Furthermore, during shade stress G. villosa also had an improved photosynthetic performance by not altering its photosynthetic LCP during reduced light conditions. It can be concluded that G. multifolia has a lower capacity than G. villosa to adapt its photosynthetic apparatus to changing environments such as increasing drought and shaded conditions. This may be a contributing factor to the threatened conservation status of G. multifolia.

South African Journal of Botany

1131936

10.1039/B402558J

Designing efficient microlens arrays: lessons from Nature

Nature provides a whole host of superior multifunctional structures that can be used as inspirational systems for the design and synthesis of new, technologically important materials and devices. We review here the exceptional optical performance of microlens arrays formed by light-sensitive brittlestars, their structural and compositional features, and advantageous properties. We show that brittlestars form a nearly perfect optical device with micron-scale, lightweight, mechanically strong, aberration-free, birefringence-free, individually-addressed lenses, which offer a unique focusing effect, signal enhancement, intensity adjustment, angular selectivity, and photochromic activity. We discuss first materials fabrication strategies that were inspired by the principles involved in the formation of echinoderm calcitic structures. The biomimetic synthetic microlens arrays could be potentially used as highly tunable optical elements for a wide variety of applications.

Journal of Materials Chemistry

2155564

10.1038/NATURE08936

A conserved spider silk domain acts as a molecular switch that controls fibre assembly

A huge variety of proteins are able to form fibrillar structures, especially at high protein concentrations. Hence, it is surprising that spider silk proteins can be stored in a soluble form at high concentrations and transformed into extremely stable fibres on demand. Silk proteins are reminiscent of amphiphilic block copolymers containing stretches of polyalanine and glycine-rich polar elements forming a repetitive core flanked by highly conserved non-repetitive amino-terminal and carboxy-terminal domains. The N-terminal domain comprises a secretion signal, but further functions remain unassigned. The C-terminal domain was implicated in the control of solubility and fibre formation initiated by changes in ionic composition and mechanical stimuli known to align the repetitive sequence elements and promote β-sheet formation. However, despite recent structural data, little is known about this remarkable behaviour in molecular detail. Here we present the solution structure of the C-terminal domain of a spider dragline silk protein and provide evidence that the structural state of this domain is essential for controlled switching between the storage and assembly forms of silk proteins. In addition, the C-terminal domain also has a role in the alignment of secondary structural features formed by the repetitive elements in the backbone of spider silk proteins, which is known to be important for the mechanical properties of the fibre.

Nature

18686597

10.1242/JEB.012146

Vortex wake and flight kinematics of a swift in cruising flight in a wind tunnel

SUMMARY In this paper we describe the flight characteristics of a swift (Apus apus) in cruising flight at three different flight speeds (8.0, 8.4 and 9.2 m s–1) in a low turbulence wind tunnel. The wingbeat kinematics were recorded by high-speed filming and the wake of the bird was visualized by digital particle image velocimetry (DPIV). Certain flight characteristics of the swift differ from those of previously studied species. As the flight speed increases, the angular velocity of the wingbeat remains constant, and so as the wingbeat amplitude increases, the frequency decreases accordingly, as though the flight muscles were contracting at a fixed rate. The wings are also comparatively inflexible and are flexed or retracted rather little during the upstroke. The upstroke is always aerodynamically active and this is reflected in the wake, where shedding of spanwise vorticity occurs throughout the wingbeat. Although the wake superficially resembles those of other birds in cruising flight, with a pair of trailing wingtip vortices connected by spanwise vortices, the continuous shedding of first positive vorticity during the downstroke and then negative vorticity during the upstroke suggests a wing whose circulation is gradually increasing and then decreasing during the wingbeat cycle. The wake (and implied wing aerodynamics) are not well described by discrete vortex loop models, but a new wake-based model, where incremental spanwise and streamwise variations of the wake impulse are integrated over the wingbeat, shows good agreement of the vertical momentum flux with the required weight support. The total drag was also estimated from the wake alone, and the calculated lift:drag ratio of approximately 13 for flapping flight is the highest measured yet for birds.

The Journal of Experimental Biology

24733699

10.1093/JXB/ERL072

The geometry of the forisome-sieve element-sieve plate complex in the phloem of Vicia faba L. leaflets.

Forisomes are contractile protein bodies that appear to control flux rates in the phloem of faboid legumes by reversibly plugging the sieve tubes. Plugging is triggered by Ca(2+) which induces an anisotropic deformation of forisomes, consisting of a longitudinal contraction and a radial expansion. By conventional light microscopy and confocal laser-scanning microscopy, the three-dimensional geometry of the forisome-sieve element-sieve plate complex in intact sieve tubes of leaflets of Vicia faba L. was reconstructed. Forisomes were mostly located close to sieve plates, and occasionally were observed drifting unrestrainedly along the sieve element, suggesting that they might be utilized as internal markers of flow direction. The diameter of forisomes in the resting state correlated with the diameter of their sieve elements, supporting the idea that radial expansion of forisomes is the geometric basis of reversible sieve tube plugging. Comparison of the present results regarding forisome geometry in situ with previously published data on forisome reactivity in vitro makes it questionable, however, whether forisomes are capable of completely sealing sieve tubes in V. faba leaves.

Journal of Experimental Botany

8765108

10.1098/RSIF.2008.0345.FOCUS

A biological sub-micron thickness optical broadband reflector characterized using both light and microwaves

Broadband optical reflectors generally function through coherent scattering from systems comprising one of three designs: overlapped; chirped; or chaotic multilayer reflectors. For each, the requirement to scatter a broad band of wavelengths is met through the presence of a variation in nanostructural periodicity running perpendicular to the systems' outer surfaces. Consequently, the requisite total thickness of the multilayer can often be in excess of 50 μm. Here, we report the discovery and the microwave-assisted characterization of a natural system that achieves excellent optical broadband reflectivity but that is less than 1 μm thick. This system, found on the wing scales of the butterfly Argyrophorus argenteus, comprises a distinctive variation in periodicity that runs parallel to the reflecting surface, rather than perpendicular to it. In this way, the requirement for an extensively thick system is removed.

Journal of the Royal Society Interface

120738437

10.1364/OME.1.000085

Visible light reflection spectra from cuticle layered materials

The brilliant metallic appearance of two kinds of beetles, the Chrysina aurigans and the Chrysina limbata, is displayed visually as well as from normalized reflection measurements of non polarized visible light under normal incidence. The C. limbata is reflective over the visible spectral wavelength range, with a silver-like aspect, while the golden-like C. aurigans is reflective for wavelengths larger than 525 nm, and with a well defined sequence of minima and maxima depicted in the reflection spectra. Both specimens show selective reflection of circular polarized light with the effect being significantly weaker for the C. limbata. A transfer matrix formalism is applied to approach the main features displayed in the measured reflection spectra, by assuming a chirped multilayer structure with decreasing thicknesses of successive layers through the cuticle of the beetles.

Optical Materials Express

16117465

10.1093/AOB/MCM184

Sympodial construction of Fibonacci-type leaf rosettes in Pinguicula moranensis (Lentibulariaceae).

BACKGROUND AND AIMS The leaf rosettes of the carnivorous Pinguicula moranensis follow a spiral phyllotaxis approaching a Fibonacci pattern while the stalked flowers arise from extra-axillary sites between the leaves. The organization of this rosette has been discussed by various authors, with various results. The aim of the present study was to clarify the development of the flowering rosettes of this species. METHODS The formation of the rosettes is shown with the aid of scanning electron microscopy. KEY RESULTS AND CONCLUSIONS The scanning electron micrographs show that each flower terminates an article (sympodial unit). The leaves of consecutive articles of such sympodially constructed rosettes are arranged along a spiral Fibonacci pattern (with divergence angles around 137 degrees). This results from homodromy of leaf initiation in consecutive articles with the first leaf (prophyll) of a new article inserted in an obliquely transverse position next to the floral scape that terminates the former article. Sympodial construction of flowering shoots and leaf rosettes is also known from Aloe, Gunnera and Philodendron. As a by-product of this study, the unidirectional development of the Pinguicula flower is confirmed and discussed.

Annals of Botany

13927823

10.1073/PNAS.1115485109

Peptide tag forming a rapid covalent bond to a protein, through engineering a bacterial adhesin

Protein interactions with peptides generally have low thermodynamic and mechanical stability. Streptococcus pyogenes fibronectin-binding protein FbaB contains a domain with a spontaneous isopeptide bond between Lys and Asp. By splitting this domain and rational engineering of the fragments, we obtained a peptide (SpyTag) which formed an amide bond to its protein partner (SpyCatcher) in minutes. Reaction occurred in high yield simply upon mixing and amidst diverse conditions of pH, temperature, and buffer. SpyTag could be fused at either terminus or internally and reacted specifically at the mammalian cell surface. Peptide binding was not reversed by boiling or competing peptide. Single-molecule dynamic force spectroscopy showed that SpyTag did not separate from SpyCatcher until the force exceeded 1 nN, where covalent bonds snap. The robust reaction conditions and irreversible linkage of SpyTag shed light on spontaneous isopeptide bond formation and should provide a targetable lock in cells and a stable module for new protein architectures.

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

137483453

10.1016/S0928-4931(99)00129-0

Radular teeth as models for the improvement of industrial cutting devices

Limpets (Gastropoda) and chitons (Polyplacophora) feed on epi- and endolithic organisms by means of the radula, a specialized feeding apparatus located in the mouth cavity. The radula owes most of its abrasive capability to the presence of numerous mineralized teeth. Here we report on the shape, internal structure, wearing pattern, feeding position, and distribution of hardness and elastic properties of these teeth in an attempt to generate ideas for the innovation of industrial cutting devices. The teeth remain sharp during their entire working-life mainly due to the fact that wearing preferentially occurs along surfaces formed by the internal structure of the tooth. It is shown that shape, internal structure, positioning and material characteristics concertedly function in minimizing the rate at which the teeth wear down and in maintaining optimal cutting behaviour. Implementation of these self-sharpening characteristics into industrial cutting devices is discussed.

Materials Science and Engineering: C

25578

10.1038/NATURE10325

Hydrogen is an energy source for hydrothermal vent symbioses

The discovery of deep-sea hydrothermal vents in 1977 revolutionized our understanding of the energy sources that fuel primary productivity on Earth. Hydrothermal vent ecosystems are dominated by animals that live in symbiosis with chemosynthetic bacteria. So far, only two energy sources have been shown to power chemosynthetic symbioses: reduced sulphur compounds and methane. Using metagenome sequencing, single-gene fluorescence in situ hybridization, immunohistochemistry, shipboard incubations and in situ mass spectrometry, we show here that the symbionts of the hydrothermal vent mussel Bathymodiolus from the Mid-Atlantic Ridge use hydrogen to power primary production. In addition, we show that the symbionts of Bathymodiolus mussels from Pacific vents have hupL, the key gene for hydrogen oxidation. Furthermore, the symbionts of other vent animals such as the tubeworm Riftia pachyptila and the shrimp Rimicaris exoculata also have hupL. We propose that the ability to use hydrogen as an energy source is widespread in hydrothermal vent symbioses, particularly at sites where hydrogen is abundant.

Nature

33207546

10.1007/S00253-002-0938-3

Biodegradation of volatile organic compounds by five fungal species

Abstract. Five fungal species, Cladosporium resinae (ATCC 34066), Cladosporium sphaerospermum (ATCC 200384), Exophiala lecanii-corni (CBS 102400), Mucor rouxii (ATCC 44260), and Phanerochaete chrysosporium (ATCC 24725), were tested for their ability to degrade nine compounds commonly found in industrial off-gas emissions. Fungal cultures inoculated on ceramic support media were provided with volatile organic compounds (VOCs) via the vapor phase as their sole carbon and energy sources. Compounds tested included aromatic hydrocarbons (benzene, ethylbenzene, toluene, and styrene), ketones (methyl ethyl ketone, methyl isobutyl ketone, and methyl propyl ketone), and organic acids (n-butyl acetate, ethyl 3-ethoxypropionate). Experiments were conducted using three pH values ranging from 3.5 to 6.5. Fungal ability to degrade each VOC was determined by observing the presence or absence of visible growth on the ceramic support medium during a 30-day test period. Results indicate that E. lecanii-corni and C. sphaerospermum can readily utilize each of the nine VOCs as a sole carbon and energy source. P. chrysosporium was able to degrade all VOCs tested except for styrene under the conditions imposed. C. resinae was able to degrade both organic acids, all of the ketones, and some of the aromatic compounds (ethylbenzene and toluene); however, it was not able to grow utilizing benzene or styrene under the conditions tested. With the VOCs tested, M. rouxii produced visible growth only when supplied with n-butyl acetate or ethyl 3-ethoxypropionate. Maximum growth for most fungi was observed at a pH of approximately 5.0. The experimental protocol utilized in these studies is a useful tool for assessing the ability of different fungal species to degrade gas-phase VOCs under conditions expected in a biofilter application.

Applied Microbiology and Biotechnology

24215344

10.1126/SCIENCE.1146421

Epoxide-Opening Cascades Promoted by Water

Selectivity rules in organic chemistry have been inferred largely from nonaqueous environments. In contrast, enzymes operate in water, and the chemical effect of the medium change remains only partially understood. Structural characterization of the “ladder” polyether marine natural products raised a puzzle that persisted for 20 years: Although the stereochemistry of adjacent tetrahydropyran (THP) cycles would seem to arise from a biosynthetic cascade of epoxide-opening reactions, experience in organic solvents argued consistently that such a pathway would be kinetically disfavored. We report that neutral water acts as an optimal promoter for the requisite ring-opening selectivity, once a single templating THP is appended to a chain of epoxides. This strategy offers a high-yielding route to the naturally occurring ladder core and highlights the likely importance of aqueous-medium effects in underpinning certain noteworthy enzymatic selectivities.

Science

205303053

10.1038/NCHEMBIO.1842

Biomaterials: Recipe for squid beak.

The molecular basis of biomaterial assembly and function can provide inspiration for new materials science designs. New research explains the squid beak's transition from soft to hard through the identification of two new families of proteins with unusual physical properties.

Nature Chemical Biology

34494254

10.1242/JEB.01530

Propulsive force calculations in swimming frogs II. Application of a vortex ring model to DPIV data

SUMMARY Frogs propel themselves by kicking water backwards using a synchronised extension of their hind limbs and webbed feet. To understand this propulsion process, we quantified the water movements and displacements resulting from swimming in the green frog Rana esculenta, applying digital particle image velocimetry (DPIV) to the frog's wake. The wake showed two vortex rings left behind by the two feet. The rings appeared to be elliptic in planform, urging for correction of the observed ring radii. The rings' long and short axes (average ratio 1.75:1) were about the same size as the length and width of the propelling frog foot and the ellipsoid mass of water accelerated with it. Average thrust forces were derived from the vortex rings, assuming all propulsive energy to be compiled in the rings. The calculated average forces (Fav=0.10±0.04 N) were in close agreement with our parallel study applying a momentum–impulse approach to water displacements during the leg extension phase. We did not find any support for previously assumed propulsion enhancement mechanisms. The feet do not clap together at the end of the power stroke and no `wedge-action' jetting is observed. Each foot accelerates its own water mantle, ending up in a separate vortex ring without interference by the other leg.

The Journal of Experimental Biology

1156804

10.1098/RSPB.2010.2784

Adaptations to in situ feeding: novel nutrient acquisition pathways in an ancient vertebrate

During feeding, hagfish may immerse themselves in the body cavities of decaying carcasses, encountering high levels of dissolved organic nutrients. We hypothesized that this feeding environment might promote nutrient acquisition by the branchial and epidermal epithelia. The potential for Pacific hagfish, Eptatretus stoutii, to absorb amino acids from the environment across the skin and gill was thus investigated. l-alanine and glycine were absorbed via specific transport pathways across both gill and skin surfaces, the first such documentation of direct organic nutrient acquisition in a vertebrate animal. Uptake occurred via distinct mechanisms with respect to concentration dependence, sodium dependence and effects of putative transport inhibitors across each epithelium. Significant differences in the absorbed amino acid distribution between the skin of juveniles and adults were noted. The ability to absorb dissolved organic matter across the skin and gill may be an adaptation to a scavenging lifestyle, allowing hagfish to maximize sporadic opportunities for organic nutrient acquisition. From an evolutionary perspective, hagfish represent a transitory state between the generalized nutrient absorption pathways of aquatic invertebrates and the more specialized digestive systems of aquatic vertebrates.

Proceedings of The Royal Society B: Biological Sciences

46591314

10.1672/0277-5212(2002)022[0430:IOSOFO]2.0.CO;2

Influence of season of fire on flowering of wet prairie grasses in south Florida, USA

We measured the effects of prescribed fire during January (dormant season) and May (growing season) on flowering of three perennial grasses, muhly (Muhlenbergia capillaris), gulfdune paspalum (Paspalum monostachyum), and south Florida bluestem (Schizachyrium rhizomatum), which are dominant grasses in wet prairies of south Florida, USA. Flowering was promoted by growing season fire but not by dormant season fire. Flowering was significantly greater for all species following prescribed fire conducted during May compared with areas burned during January of the same calendar year. The strong positive effect of growing season fire on flowering of all three species decreased after the first growing season. We rejected the hypothesis that season of fire did not influence flowering. Our results indicated that flowering by these dominant, wet prairie grasses is promoted by early growing season fire, which corresponds to historical patterns of lightning-ignited fire in south Florida.

Wetlands

8962045

10.1086/673889

The Anatomy and Histology of Caudal Autotomy and Regeneration in Lizards*

Caudal autotomy—the ability to self-detach the tail—is a dramatic adaptation common to many structural-grade lizards. For most species, tail loss is followed by the equally dramatic phenomenon of tail regeneration. Here we review the anatomy and histology of caudal autotomy and regeneration in lizards, drawing heavily from research published over the past 2 decades. The autotomous tail is characterized by various structural adaptations, which act to minimize blood loss and trauma to adjacent tissues. The early phase of wound healing involves a leukocytic response but limited inflammation. Reepithelialization via a specialized wound epithelium is not only critical for scar-free healing but also necessary for subsequent tissue patterning and regenerative outgrowth. Regeneration begins with the formation of the blastema, a mass of proliferating mesenchymal-like cells. As the blastema expands, it is invaded by blood vessels and the spinal cord. Whereas the replacement tail outwardly resembles the original appendage, it differs in several notable respects, including the tissue composition and organization of the skeleton, muscular system, and spinal cord. Increasingly, the lizard tail is being recognized among biomedical scientists as an important model for the study of wound healing and multitissue restoration.

Physiological and Biochemical Zoology

85419381

10.1016/0022-0981(94)90019-1

Do anemonefishes use molecular mimicry to avoid being stung by host anemones

Anemonefishes are known to have a protective mucous coat that allows them to contact the tentacles of their host anemone without being stung. There are two conflicting hypotheses as to the source and biochemical properties of this mucous coating. One hypothesis proposes that anemonefishes acquire anemone substances from their hosts during the behavioral process of acclimation, that protect the fish from being stung. Anemonefishes are considered to use anemone mucus as “chemical camouflage” or “macromolecular mimicry” to avoid recognition as “not-self” by the anemone, and possible subsequent stinging. Another hypothesis is that anemonefishes produce their own protective mucus coat, which lacks substances that elicit cnida (nematocyst and spirocyst) discharge by their hosts. The present study used immunological techniques to test whether the anemonefish Amphiprion clarkii (Bennett) (which was innately protected from two of the anemones used in the present study) has a mucous coat that resembles the external mucus of anemones. Polyclonal antibodies were prepared to the mucus of four species of anemones [Heteractis crispa, (Ehrenberg) Stichodactyla haddoni (Saville-Kent), Macrodactyla doreenensis (Quoy and Gaimard), and Condylactis gigantea (Weinland)]. Ouchterlony (double immunodiffusion) tests showed that different antigens were present in the mucus of the four anemone species. Anemone antigens were not detected in the mucous coating of either naive (fish that had never before encountered sea anemones) or associated (those living with sea anemones) anemonefishes in Ouchterlony tests. However, more sensitive ELISA (enzyme-linked immunosorbent assay) tests showed that anemone mucus antigens were present in the mucous coating of associated anemonefish, but not naive fish. This showed that an innately protected A. clarkii does not produce a mucus coat that is biochemically similar to that of anemones, but that the same fish does acquire anemone substances in its mucus coat when it associates with anemones in aquaria. It remains to be shown whether these anemone substances actually provide the initial protection for those anemonefishes that must undergo acclimation behavior in order to keep from being stung by their host sea anemones, or additional protection for innately protected fishes.

Journal of Experimental Marine Biology and Ecology

86058104

10.2307/1936377

The Role of Seed Banks in the Vegetation Dynamics of Prairie Glacial Marshes

The presence of viable seed in 24 substrate samples from Eagle Lake, a marsh in north- central Iowa, was tested by placing subsamples of each sample under 2 environmental conditions. One set of subsamples was placed underwater (submersed treatment). Seeds of 20 species germinated and grew in this treatment. On the average, there were 8.3 species/sample. The 2nd set of subsamples was kept moist, simulating conditions on an exposed mud flat (drawdown treatment). In the drawdown treatment, on the average, seeds of 12.9 species germinated/sample. Altogether seeds of 40 species germinated in this treatment of which only 24% were also found in the submersed treatment. By combining the results from the 2 treatments, the seed banks in the 6 vegetation types studied were estimated to range from 21,445 to 42,615 seeds/m2 on the average in the upper 5 cm of soil. Field studies at Eagle Lake (1974) and Goose Lake (1976), when these marshes had no standing water, revealed that the most abundant species whose seeds germinated on exposed mud flats were the same as the most abundant species in the experimental drawdown samples from Eagle Lake. In 1975, when Eagle Lake had standing water again, the submersed and floating species that were found were the same as those found in the experimental submersed samples from Eagle Lake. The seed-bank results and vegetation sampling reveal that there are 3 types of species present in prairie marsh seed banks: emergent species (Typha, Scirpus, Sparganium, Sagittaria) germinate on exposed mud flats or in very shallow water; submersed and free-floating species (Lemna, Spirodela, Ceratophyllum, Naias, Potamogeton) whose dormant seeds or turions can survive on exposed mud flats for a year and which germinate when there is standing water; and mud-flat species (Bidens, Cyperus, Polygonum and Rumex) which are ephemerals whose seeds can only germinate on exposed mud flats during periods when no standing water exists in the marsh because of drought or water level manipulation. When the marsh refloods, these species are eliminated from the visible marsh flora. Primarily because of fluctuating water levels and muskrat damage, prairie marshes have cyclical changes in their vegetation during which mud-flat, emergent, or submersed and free-floating species replace each other as the dominant type of species in a marsh.

Ecology

4324728

10.1038/NATURE08729

Directional water collection on wetted spider silk

Many biological surfaces in both the plant and animal kingdom possess unusual structural features at the micro- and nanometre-scale that control their interaction with water and hence wettability. An intriguing example is provided by desert beetles, which use micrometre-sized patterns of hydrophobic and hydrophilic regions on their backs to capture water from humid air. As anyone who has admired spider webs adorned with dew drops will appreciate, spider silk is also capable of efficiently collecting water from air. Here we show that the water-collecting ability of the capture silk of the cribellate spider Uloborus walckenaerius is the result of a unique fibre structure that forms after wetting, with the ‘wet-rebuilt’ fibres characterized by periodic spindle-knots made of random nanofibrils and separated by joints made of aligned nanofibrils. These structural features result in a surface energy gradient between the spindle-knots and the joints and also in a difference in Laplace pressure, with both factors acting together to achieve continuous condensation and directional collection of water drops around spindle-knots. Submillimetre-sized liquid drops have been driven by surface energy gradients or a difference in Laplace pressure, but until now neither force on its own has been used to overcome the larger hysteresis effects that make the movement of micrometre-sized drops more difficult. By tapping into both driving forces, spider silk achieves this task. Inspired by this finding, we designed artificial fibres that mimic the structural features of silk and exhibit its directional water-collecting ability.

Nature

43568708

10.1007/BF00312146

Domes, arches and urchins: The skeletal architecture of echinoids (Echinodermata)

SummaryA combination of simple membrane theory and statical analysis has been used to determine how stresses are carried in echinoid skeletons. Sutures oriented circumferentially are subject principally to compression. Those forming radial zig-zags are subject to compression near the apex and tension near the ambitus. Radial and circumferential sutures in Eucidaris are equally bound with collagen fibers but in Diadema, Tripneustes, Psammechinus, Arbacia and other regular echinoids, most radial sutures are more heavily bound, and thus stronger in tension. Psammechinus, Tripneustes and several other echinoids have radial sutures thickened by ribs which increase the area of interlocking trabeculae. Ribs also increase flexural stiffness and carry a greater proportion of the stress. Further, ribs effectively draw stress from weaker areas pierced by podial pores, and increase the total load which can be sustained.Allometry indicates that regular echinoids become relatively higher at the apex as size increases, thus reducing ambital stresses. Some spatangoids with very high domes (eg Agassizia) maintain isometry, but others (eg Meoma) become flatter with size. Both holectypoids (Echinoneus) and cassiduloids (Apatopygus) maintain a constant height to diameter relationship. Flattening, and consequently ambital tensile stress, is greatest in the clypeasteroids. In this group the formation of internal buttresses which preferentially carry stress, reaches maximum development. A notable exception, however, is the high domed Clypeaster rosaceus.In this analysis it was assumed that local buckling or bending does not occur. The test of some echinoids (e.g. Diadematoida) have relatively wide sutures swathed in collagen, which allows local deformation. Others (e.g. Arbacia) have rigid sutures with reduced collagen. In Psammechinus and other members of the Order Echinoida, in addition to rib formation, inner and outer surface trabeculae are thickened so that the individual plates are stiffened. Some spatangoids (Meoma, Paleopneustes) have extensive sutural collagen, but the cassiduloid Apatopygus has collagen confined to junctions of sutures, and elsewhere the joints are strengthened and stiffened by fusion of trabeculae. Fusion of surface trabeculae is almost complete in the holectypoid, Echinoneus, and the sutures are obscured.

Zoomorphology

28284165

10.1126/SCIENCE.1063724

Lobster Sniffing: Antennule Design and Hydrodynamic Filtering of Information in an Odor Plume

The first step in processing olfactory information, before neural filtering, is the physical capture of odor molecules from the surrounding fluid. Many animals capture odors from turbulent water currents or wind using antennae that bear chemosensory hairs. We used planar laser–induced fluorescence to reveal how lobster olfactory antennules hydrodynamically alter the spatiotemporal patterns of concentration in turbulent odor plumes. As antennules flick, water penetrates their chemosensory hair array during the fast downstroke, carrying fine-scale patterns of concentration into the receptor area. This spatial pattern, blurred by flow along the antennule during the downstroke, is retained during the slower return stroke and is not shed until the next flick.

Science

7338695

10.1016/J.BIOSYSTEMS.2006.09.027

Directional hearing in a silicon cricket

Phonotaxis is the ability to orient towards or away from sound sources. Crickets can locate conspecifics by phonotaxis to the calling (mating) song they produce, and can evade bats by negative phonotaxis from echolocation calls. The behaviour and underlying physiology have been studied in some depth, and the auditory system solves this complex problem in a unique manner. Experiments conducted on a simulation model of the system indicated that the mechanism output a directional signal to sounds ahead at calling song frequency and to sounds behind at echolocation frequencies. We suggest that this combination of responses helps simplify later processing in the cricket. To further explore this result, an analogue, very large scale integrated (aVLSI) circuit model of the mechanism was designed and built; results from testing this agreed with the simulation. The aVLSI circuit was used to test a further hypothesis about the potential advantages of the positioning of the acoustic inputs for sound localisation during walking. There was no clear advantage to the directionality of the system in their location. The aVLSI circuitry is now being extended to use on a robot along with previously modelled neural circuitry to better understand the complete sensorimotor pathway.

BioSystems

41342994

10.1126/SCIENCE.204.4391.415

Natural Polyesters: Dufour's Gland Macrocyclic Lactones Form Brood Cell Laminesters in Colletes Bees

Bees in the genus Colletes make their brood cells in the ground and coat them with a highly resistant, waterproof, transparent membrane. This membrane is a polyester constructed mainly from 18-hydroxyoctadecanoic acid and 20-hydroxy-eicosanoic acid, which are stored as their corresponding lactones in the Dufour's gland of the bee. When lining the cells, the bee secretes its glandular content, and the membrane is apparently a product of polycondensation reaction of its contents. This appears to be the first report of a naturally occurring linear polyester. The term laminester (lamina ≃ layer + ester) for this class of compounds is proposed.

Science

20722620

10.1079/SSR2002112

Sacred lotus, the long-living fruits of China Antique

In the West, lotus (Nelumbo nucifera Gaertn.) is relatively little known. However, for more than 3000 years, lotus plants have been cultivated as a crop in Far-East Asia, where they are used for food, medicine and play a significant role in religious and cultural activities. Holder of the world’s record for long-term seed viability (1300 years) is a lotus fruit (China Antique) from Xipaozi, Liaoning Province, China. Five offspring of this variety, from 200–500-year-old fruits (14C dates) collected at Xipaozi, have recently been germinated, and are the first such seedlings to be raised from directly dated fruits. The fruits at Xipaozi, preserved in a dry ancient lakebed, have been exposed to low-dose γ-radiation for hundreds of years (having an accumulated soil irradiation of 0.1–1.0 Gy). Offspring from these old fruits show abnormalities that resemble those in various modern seedlings irradiated at much higher doses. Although these lotus offspring are phenotypically abnormal, the viability of old seeds was evidently not affected by accumulated doses of up to 3 Gy. Growth characteristics of first- and second-year lotus offspring of these fruits, products of the longest-term radiobiological experiment on record, are summarized here (rapid early growth, phenotypic abnormalities, lack of vigour, poor rhizome development and low photosynthetic activity during second-year growth). Aspects of their chromosomal organization, phenotype and physiology (rapid recovery from stress, heat-stable proteins, protein-repair enzyme) are discussed. Important unsolved problems are suggested to elicit interest among members of the seed science community to the study of old fruits recently collected at Xipaozi, with particular emphasis on aspects of ageing and repair.

Seed Science Research

25172911

10.1242/JEB.062620

Kingfisher feathers – colouration by pigments, spongy nanostructures and thin films

SUMMARY The colours of the common kingfisher, Alcedo atthis, reside in the barbs of the three main types of feather: the orange breast feathers, the cyan back feathers and the blue tail feathers. Scanning electron microscopy showed that the orange barbs contain small pigment granules. The cyan and blue barbs contain spongy nanostructures with slightly different dimensions, causing different reflectance spectra. Imaging scatterometry showed that the pigmented barbs create a diffuse orange scattering and the spongy barb structures create iridescence. The extent of the angle-dependent light scattering increases with decreasing wavelength. All barbs have a cortical envelope with a thickness of a few micrometres. The reflectance spectra of the cortex of the barbs show oscillations when measured from small areas, but when measured from larger areas the spectra become wavelength independent. This can be directly understood with thin film modelling, assuming a somewhat variable cortex thickness. The cortex reflectance appears to be small but not negligible with respect to the pigmentary and structural barb reflectance.

The Journal of Experimental Biology

205252712

10.1073/PNAS.1100701108

Exopolymer alteration of physical properties of sea ice and implications for ice habitability and biogeochemistry in a warmer Arctic

The physical properties of Arctic sea ice determine its habitability. Whether ice-dwelling organisms can change those properties has rarely been addressed. Following discovery that sea ice contains an abundance of gelatinous extracellular polymeric substances (EPS), we examined the effects of algal EPS on the microstructure and salt retention of ice grown from saline solutions containing EPS from a culture of the sea-ice diatom, Melosira arctica. We also experimented with xanthan gum and with EPS from a culture of the cold-adapted bacterium Colwellia psychrerythraea strain 34H. Quantitative microscopic analyses of the artificial ice containing Melosira EPS revealed convoluted ice-pore morphologies of high fractal dimension, mimicking features found in EPS-rich coastal sea ice, whereas EPS-free (control) ice featured much simpler pore geometries. A heat-sensitive glycoprotein fraction of Melosira EPS accounted for complex pore morphologies. Although all tested forms of EPS increased bulk ice salinity (by 11–59%) above the controls, ice containing native Melosira EPS retained the most salt. EPS effects on ice and pore microstructure improve sea ice habitability, survivability, and potential for increased primary productivity, even as they may alter the persistence and biogeochemical imprint of sea ice on the surface ocean in a warming climate.

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

84703114

10.2307/2260070

Self-burial behaviour of Erodium cicutarium seeds.

(1) The self-planting mechanism of the hygroscopic 'seeds' of Erodium cicutarium was examined. (2) Burial depended first on the location of crevices by the seeds. (3) The seeds were more likely to establish themselves in large crevices, even when their awn-tails, awn-hairs and carpel-tips had been removed experimentally. (4) Once in a crevice, the probability of a seed remaining there and the depth attained were greater when the crevices were small. In small crevices, seeds with intact awns and carpels attained greater depths than that of those without these structures. (5) When crevices were small and common, the seeds became established after five uncoiling-recoiling cycles. In large crevices, eight cycles were required for establishment; when crevices were small and infrequent, forty cycles were required.

Journal of Ecology

26838200

10.1007/S004350050084

Evolution of the metathoracic tympanal ear and its mesothoracic homologue in the Macrolepidoptera (Insecta)

Abstract Two independent methods of comparison, serial homology and phylogenetic character mapping, are employed to investigate the evolutionary origin of the noctuoid moth (Noctuoidea) ear sensory organ. First, neurobiotin and Janus green B staining techniques are used to describe a novel mesothoracic chordotonal organ in the hawkmoth, Manduca sexta, which is shown to be serially homologous to the noctuoid metathoracic tympanal organ. This chordotonal organ comprises a proximal scolopidial region with three bipolar sensory cells, and a long flexible strand (composed of attachment cells) that connects peripherally to an unspecialized membrane ventral to the axillary cord of the fore-wing. Homology to the tympanal chordotonal organ in the Noctuoidea is proposed from anatomical comparisons of the meso- and metathoracic nerve branches and their corresponding peripheral attachment sites. Second, the general structure (noting sensory cell numbers, gross anatomy, and location of peripheral attachment sites) of both meso- and metathoracic organs is surveyed in 23 species representing seven superfamilies of the Lepidoptera. The structure of the wing-hinge chordotonal organ in both thoracic segments was found to be remarkably conserved in all superfamilies of the Macrolepidoptera examined except the Noctuoidea, where fewer than three cells occur in the metathoracic ear (one cell in representatives of the Notodontidae and two cells in those of other families examined), and at the mesothoracic wing-hinge (two cells) in the Notodontidae only. By mapping cell numbers onto current phylogenies of the Macrolepidoptera, we demonstrate that the three-celled wing-hinge chordotonal organ, believed to be a wing proprioceptor, represents the plesiomorphic state from which the tympanal organ in the Noctuoidea evolved. This ’trend toward simplicity’ in the noctuoid ear contrasts an apparent ’trend toward complexity’ in several other insect hearing organs where atympanate homologues have been studied. The advantages to having fewer rather than more cells in the moth ear, which functions primarily to detect the echolocation calls of bats, is discussed.

Zoomorphology

24087816

10.1074/JBC.270.47.28169

Use of an Oligoribonucleotide Containing the Polypurine Tract Sequence as a Primer by HIV Reverse Transcriptase (*)

A primary site for initiation of plus strand DNA synthesis in human immunodeficiency virus (HIV) corresponds to a 19-nucleotide-long purine rich sequence located just upstream of the U3 region, designated the polypurine tract (PPT). The HIV reverse transcriptase (RT) uses its RNase H activity to cut the genomic RNA after minus strand DNA synthesis. A plus strand PPT primer is formed, extended, and then removed. In vitro, the HIV-RT recognizes this primer specifically, using it much more efficiently than other RNA primers. However, the PPT still primes significantly less efficiently than DNA primers. The 19-nucleotide PPT primer is partially resistant to degradation when compared with other oligoribonucleotides. Prior to initiation of DNA synthesis, several nucleotides are removed by the RT from the 3′ ends of some of the PPT primers. Cleavage is enhanced in the absence of dNTPs. We suggest that DNA synthesis suppresses primer degradation, so that primer extension and cleavage occur in proper sequence. As a result of 3′ end degradation, PPT elongation products contain 5′-RNA segments from 16 to 19 nucleotides in length. These shorter segments are also generated from a longer transcript containing the PPT sequence, indicating that they are not created as a result of binding of the RT to the 5′ end of the PPT oligoribonucleotide. Full-length and shorter versions of the PPT primers are cleaved from the extended DNA by RT. These experiments show that HIV-RT has a specificity to generate a primer in the region of the PPT but that the ends of the primer are not well defined.

Journal of Biological Chemistry

42054256

10.1099/00221287-146-12-3237

How Delisea pulchra furanones affect quorum sensing and swarming motility in Serratia liquefaciens MG1.

Halogenated furanones produced by the benthic marine macroalga Delisea pulchra inhibit swarming motility of Serratia liquefaciens MG1. This study demonstrates that exogenously added furanones control transcription of the quorum sensing regulated gene swrA in competition with the cognate signal molecule N:-butanoyl-L-homoserine lactone. This in turn results in reduced production of the surface-active compound serrawettin W2, which is crucial for surface translocation of the differentiated swarm cells. It is demonstrated that furanones interfere with interspecies communication during swarming of mixed cultures and that the mode of interference in quorum-sensing control and interspecies communication is not through inhibition of autoinducer synthesis.

Microbiology

3807424

10.1371/JOURNAL.PONE.0007298

Coral Fluorescent Proteins as Antioxidants

Background A wide array of fluorescent proteins (FP) is present in anthozoans, although their biochemical characteristics and function in host tissue remain to be determined. Upregulation of FP's frequently occurs in injured or compromised coral tissue, suggesting a potential role of coral FPs in host stress responses. Methodology/Principal Findings The presence of FPs was determined and quantified for a subsample of seven healthy Caribbean coral species using spectral emission analysis of tissue extracts. FP concentration was correlated with the in vivo antioxidant potential of the tissue extracts by quantifying the hydrogen peroxide (H2O2) scavenging rates. FPs of the seven species varied in both type and abundance and demonstrated a positive correlation between H2O2 scavenging rate and FP concentration. To validate this data, the H2O2 scavenging rates of four pure scleractinian FPs, cyan (CFP), green (GFP), red (RFP) and chromoprotein (CP), and their mutant counterparts (without chromophores), were investigated. In vitro, each FP scavenged H2O2 with the most efficient being CP followed by equivalent activity of CFP and RFP. Scavenging was significantly higher in all mutant counterparts. Conclusions/Significance Both naturally occurring and pure coral FPs have significant H2O2 scavenging activity. The higher scavenging rate of RFP and the CP in vitro is consistent with observed increases of these specific FPs in areas of compromised coral tissue. However, the greater scavenging ability of the mutant counterparts suggests additional roles of scleractinian FPs, potentially pertaining to their color. This study documents H2O2 scavenging of scleractinian FPs, a novel biochemical characteristic, both in vivo across multiple species and in vitro with purified proteins. These data support a role for FPs in coral stress and immune responses and highlights the multi-functionality of these conspicuous proteins.

PLOS ONE

42687285

10.1111/1365-2656.12057

Does cooperation increase helpers' later success as breeders? A test of the skills hypothesis in the cooperatively displaying lance-tailed manakin.

Experience improves individual performance in many tasks. Pre-breeding cooperation may provide important experience that improves later success as a breeder, offering one compelling explanation for why some individuals delay reproduction to help others breed (the 'skills hypothesis'). However, confounding effects of age, quality and alternative selective benefits have complicated rigorous tests of this hypothesis. Male lance-tailed manakins perform cooperative courtship displays involving partnerships between unrelated alpha and beta males, and alphas monopolize resulting copulations. Beta males therefore do not receive immediate direct or indirect fitness benefits, but may gain skills during cooperation that increase their later success as an alpha. To date, however, the effect of cooperative experience on later success as a breeder has never been tested in any cooperatively displaying taxon. The effects of prior cooperative experience on reproductive success of alpha lance-tailed manakins were analysed in a mixed model framework using 12 years of information on cooperative experience and annual and lifetime genetic reproductive success for 57 alpha males. Models included previously identified effects of age and alpha tenure. Individual-level random effects controlled for quality differences to test for an independent influence of beta experience on success. Males accumulated up to 5 years of beta experience before becoming alphas, but 42·1% of alphas had no prior beta experience. Betas became alphas later in life, and experienced significantly lower reproductive success in their final year as alpha than males that were never beta, but did not have higher lifetime success or longer alpha tenures. Differences in patterns of annual siring success were best explained by age-dependent patterns of reproductive improvement and senescence among alphas, not beta experience. Cooperative experience does not increase relative breeding success for male lance-tailed manakins. Importantly, beta cooperation seems to be an alternative reproductive tactic that yields fitness payoffs equivalent to a non-cooperative route to alpha status, if population growth rate is stable.

Journal of Animal Ecology

10877277

10.1016/J.BBAPAP.2008.08.012

Acetogenesis and the Wood-Ljungdahl pathway of CO(2) fixation.

Conceptually, the simplest way to synthesize an organic molecule is to construct it one carbon at a time. The Wood-Ljungdahl pathway of CO(2) fixation involves this type of stepwise process. The biochemical events that underlie the condensation of two one-carbon units to form the two-carbon compound, acetate, have intrigued chemists, biochemists, and microbiologists for many decades. We begin this review with a description of the biology of acetogenesis. Then, we provide a short history of the important discoveries that have led to the identification of the key components and steps of this usual mechanism of CO and CO(2) fixation. In this historical perspective, we have included reflections that hopefully will sketch the landscape of the controversies, hypotheses, and opinions that led to the key experiments and discoveries. We then describe the properties of the genes and enzymes involved in the pathway and conclude with a section describing some major questions that remain unanswered.

Biochimica et Biophysica Acta

84688023

10.1016/J.JCZ.2005.11.001

The functional morphology and attachment mechanism of pandarid adhesion pads (Crustacea: Copepoda: Pandaridae)

Abstract The attachment mechanism of pandarid adhesion pads is described from observations of their externally ridged structure and internal construction in three species; Pandarus bicolor Leach, 1816, Dinemoura latifolia (Steenstrup and Lutken, 1861) and Echthrogaleus coleoptratus (Guerin-Meneville, 1837). The host's external skin morphology was also examined, since parasite attachment mechanism and host surface can be considered as components of a single system. The results emphasise the importance of the physical nature of the pad's surface. This is inferred from the compliance of the cuticle and subsurface structure, and the presence of cuticular ridging. The pads probably prevent pandarids from being dislodged by hydrodynamic drag, by increasing overall adhesion. It is proposed that this is achieved in different ways, by two types of adhesion pad identified here, distinguishable by their external structure and location. Type I pads are suggested to remove interfacial water and increase surface contact by one of two contrasting methods. The ridges may act as tyre treads, by channelling water from the contact surface. Alternatively, the channels between ridges may be hydrophobic and behave as dewetting structures, preventing water from entering in the same way that troughs between surface nodules function to produce superhydrophobicity on lotus leaves. Type I adhesion pads are also suggested to aid attachment by hindering the process of peeling, by which they are thought to be removed by hydrodynamic drag. Type II pads are more likely to function as one-way frictional attachments. Both types of pad appear to be attached passively, since they lack muscles inserting into them. The adhesive mechanism of each, which functions most effectively on hard surfaces, may explain why pads are absent or reduced on pandarids which parasitise the softer, unscaled surfaces of hosts. Pandarids predominantly parasitise the skin and fins of fast-swimming sharks. This may be because the scales are characteristically smaller in these species and are more easily encircled by the primary attachment appendages, the maxillipeds. This is thought to be the first published report to reveal frictional attachment structures from the Crustacea, which have convergently evolved in many terrestrial Arthropoda.

Zoologischer Anzeiger – A Journal of Comparative Zoology

34516053

10.1126/SCIENCE.982027

Jackrabbit ears: surface temperatures and vascular responses.

Blood flow to the ear pinnae is curtailed at ambient temperatures of between 1.4 degrees and 24 degrees C, which minimizes heat loss across the pinnae and allows the surfaces of erect pinnae to approach ambient temperature. The pinnae are warmed by steady or pulsatile vasodilation in some animals when the ambient temperature is between 1 degree and 9 degrees C below body temperature, a response favoring heat loss. When ambient temperature exceeds body temperature by 4 degrees to 5 degrees C, the pinnae are circulated with blood cooler than ambient temperature; this response favors heat influx.

Science

85099263

10.1111/IBI.12272

The winter diet of the Atlantic Puffin Fratercula arctica around the Faroe Islands

Most mortality of Atlantic Puffins occurs outside the breeding season but little is known about the species’ diet at that time. The stomach contents of 176 Puffins shot legally for food around the Faroe Islands between October and January in three winters were examined. The remains of 20 species of fish, six species of crustacea and single species of polychaete, chaetognathid and squid were identified. The most frequently recorded prey in terms of frequency of occurrence were 0 group (<1 year old) Lesser Sandeel Ammodytes marinus (82% of stomachs), followed by mesopelagic fish (52%), nereid worms (41%), Silver Rockling Gaidropsarus argentatus (36%), crustacea (35%), large sandeel (32%) and other large fish (32%). In terms of calculated biomass, nereids (41%), large sandeel (23%) and other large fish (17%) made up the bulk of the diet but the latter two prey types were most important in energetic terms (46% despite accounting for only 9% of items). Stomach contents collected on the same day and location were significantly more similar than those collected on different dates and locations, suggesting that during the winter, Puffins are generalists, taking any prey they encounter.

Ibis

4412354

10.1038/NATURE06101

The detection of carbonation by the Drosophila gustatory system

There are five known taste modalities in humans: sweet, bitter, sour, salty and umami (the taste of monosodium glutamate). Although the fruitfly Drosophila melanogaster tastes sugars, salts and noxious chemicals, the nature and number of taste modalities in this organism is not clear. Previous studies have identified one taste cell population marked by the gustatory receptor gene Gr5a that detects sugars, and a second population marked by Gr66a that detects bitter compounds. Here we identify a novel taste modality in this insect: the taste of carbonated water. We use a combination of anatomical, calcium imaging and behavioural approaches to identify a population of taste neurons that detects CO2 and mediates taste acceptance behaviour. The taste of carbonation may allow Drosophila to detect and obtain nutrients from growing microorganisms. Whereas CO2 detection by the olfactory system mediates avoidance, CO2 detection by the gustatory system mediates acceptance behaviour, demonstrating that the context of CO2 determines appropriate behaviour. This work opens up the possibility that the taste of carbonation may also exist in other organisms.

Nature

17293184

10.1242/JEB.00848

Force production and flow structure of the leading edge vortex on flapping wings at high and low Reynolds numbers

SUMMARY The elevated aerodynamic performance of insects has been attributed in part to the generation and maintenance of a stable region of vorticity known as the leading edge vortex (LEV). One explanation for the stability of the LEV is that spiraling axial flow within the vortex core drains energy into the tip vortex, forming a leading-edge spiral vortex analogous to the flow structure generated by delta wing aircraft. However, whereas spiral flow is a conspicuous feature of flapping wings at Reynolds numbers (Re) of 5000, similar experiments at Re=100 failed to identify a comparable structure. We used a dynamically scaled robot to investigate both the forces and the flows created by a wing undergoing identical motion at Re of∼ 120 and ∼1400. In both cases, motion at constant angular velocity and fixed angle of attack generated a stable LEV with no evidence of shedding. At Re=1400, flow visualization indicated an intense narrow region of spanwise flow within the core of the LEV, a feature conspicuously absent at Re=120. The results suggest that the transport of vorticity from the leading edge to the wake that permits prolonged vortex attachment takes different forms at different Re.

The Journal of Experimental Biology

54906571

10.1016/S1369-7021(10)70016-X

Analysis of an ultra hard magnetic biomineral in chiton radular teeth

Recent analyses of the ultrastructural and mechanical properties of mineralized biological materials have demonstrated some common architectural features that can help explain their observed damage tolerance. Nature has accomplished this feat through the precise control of anisotropic crystal nucleation and growth processes in conjunction with nanoscale control over the self-assembly of spatially distinct organic and inorganic phases, resulting in effective inhibition of crack propagation through these materials. One such example is found in the hyper-mineralized and abrasion resistant radular teeth of the chitons, a group of herbivorous marine mollusks who have the surprising capacity to erode away the rocky substrates on which they graze 1-4 . Through the use of modern microscopy and nanomechanical characterization techniques, we describe the architectural and mechanical properties of the radular teeth from Cryptochiton stelleri. Chiton teeth are shown to exhibit the largest hardness and stiffness of any biominerals reported to date, being notably as much as three-fold harder than human enamel and the calcium carbonate-based shells of mollusks. We explain how the unique multi-phasic design of these materials contributes not only to their functionality, but also highlights some interesting design principles that might be applied to the fabrication of synthetic composites.

Materials Today

18138173

10.1016/J.CUB.2012.04.051

Intraspecific Directed Deterrence by the Mustard Oil Bomb in a Desert Plant

Plant secondary metabolites (SMs) acting as defensive chemicals in reproductive organs such as fruit tissues play roles in both mutualistic and antagonistic interactions between plants and seed dispersers/predators. The directed-deterrence hypothesis states that SMs in ripe fruits deter seed predators but have little or no effect on seed dispersers. Indeed, studies have demonstrated that birds are able to cope with fruit SMs whereas rodents are deterred by them. However, this mechanism was only demonstrated at the class level, i.e., between birds and mammals, based on differences in the vanilloid receptors. Here we present experimental and behavioral data demonstrating the use of the broad-range, class-independent "mustard oil bomb" mechanism in Ochradenus baccatus fruits to force a behavioral change at an ecological timescale, converting rodents from seed predators to seed dispersers. This is achieved by a unique compartmentalization of the mustard oil bomb, causing activation of the system only upon seed and pulp coconsumption, encouraging seed dispersal via seed spitting by rodents. Our findings demonstrate the power of SMs to shift the animal-plant relationship from predation to mutualism and provide support for the directed-deterrence hypothesis at the intraspecific level, in addition to the interspecific level.

Current Biology

85721181

10.2307/1309104

Water Transport by Sandgrouse

Water transport in the feathers of birds is not unique to the sandgrouse, but the sandgrouse have developed the technique to a stage far beyond that of any other bird. That this should have happened in birds of arid zones is not surprising; what is not immediately obvious is how it happened. The first documented accounts of water transport in sandgrouse are of captive males carrying water in their belly feathers to their young (Meade-Waldo 1896, 1897, 1906, 1921, St. Quintin 1905). These observations were disbelieved and discredited by later ornithologists (e.g., Hile and Etch6copar 1957, Meinertzhagen 1954, Stegmann 1969). Meinertzhagen even went so far as to initiate the myth that the male sandgrouse regurgitates water from his crop to the incubating female and that both sexes provide their young with water in this way. This has since proven to be patently untrue. Why it should have been necessary to fabricate a story when the truth was so much more fascinating and worthy of investigation, is hard to understand.

BioScience

136600111

10.1002/ADEM.201180027

Battle in the Amazon: Arapaima versus Piranha

The scales of the Arapaimas, a large freshwater fish (up to 200 kg), are a superb example of a natural material that has evolved to provide protection against predators. The Arapaimas lives primarily in Amazon basin lakes that become infested with piranhas as the dry season advances and is covered with scales having up to 10 cm length. They have a collagen interior with a highly mineralized external layer. The collagen fibers form a cross-lamellar arrangement which produces a laminate composite. The internal collagenous layer provides the flexibility to the scales, which can undergo significant elastic deformation prior to failure, providing considerable toughness. The mineralized exterior provides the required protection against predation. The flexibility of the biomineral is enabled by two factors: (i) a corrugated configuration in which the tensile strains are minimized; (ii) a graded composition. We propose herein that the structure of the scales, a composite consisting of a mineralized external layer with surface corrugations and an internal flexible collagenous foundation, can serve as inspiration for the design of flexible composites having a hard ceramic surface. The piranha (Serrasalminae) is one of the principal predators in seasonal lakes, in which fish get trapped. Its teeth form triangular arrays creating a guillotine action that is highly effective in slicing through muscle. The bite force is calculated for a piranha with a mass of 1 kg from estimated maximum force values applied by three muscle groups connecting the jaw to the mandible: it is ≈20 N. Mechanical tests on the scales and teeth demonstrate that the cutting and puncturing ability of the piranha teeth cannot penetrate the Arapaimas scales.

Advanced Engineering Materials

206057366

10.1111/JFB.12705

Biological characterization of the skin of shortfin mako shark Isurus oxyrinchus and preliminary study of the hydrodynamic behaviour through computational fluid dynamics.

This study characterized the morphology, density and orientation of the dermal denticles along the body of a shortfin mako shark Isurus oxyrinchus and identified the hydrodynamic parameters of its body through a computational fluid-dynamics model. The study showed a great variability in the morphology, size, shape, orientation and density of dermal denticles along the body of I. oxyrinchus. There was a significant higher density in dorsal and ventral areas of the body and their highest angular deviations were found in the lower part of the mouth and in the areas between the pre-caudal pit and the second dorsal and pelvic fins. A detailed three-dimensional geometry from a scanned body of a shark was carried out to evaluate the hydrodynamic properties such as drag coefficient, lift coefficient and superficial (skin) friction coefficient of the skin together with flow velocity field, according to different roughness coefficients simulating the effect of the dermal denticles. This preliminary approach contributed to detailed information of the denticle interactions. As the height of the denticles was increased, flow velocity and the effect of lift decreased whereas drag increased. The highest peaks of skin friction coefficient were observed around the pectoral fins.

Journal of Fish Biology

25734824

10.1038/JID.2001.1

Skin barrier structure and function: the single gel phase model.

A new model for the structure and function of the mammalian skin barrier is postulated. It is proposed that the skin barrier, i.e., the intercellular lipid within the stratum corneum, exists as a single and coherent lamellar gel phase. This membrane structure is stabilized by the very particular lipid composition and lipid chain length distributions of the stratum corneum intercellular space and has virtually no phase boundaries. The intact, i.e., unperturbed, single and coherent lamellar gel phase is proposed to be mainly located at the lower half of stratum corneum. Further up, crystalline segregation and phase separation may occur as a result of the desquamation process. The single gel phase model differs significantly from earlier models in that it predicts that no phase separation, neither between liquid crystalline and gel phases nor between different crystalline phases with hexagonal and orthorhombic chain packing, respectively, is present in the unperturbed barrier structure. The new skin barrier model may explain: (i) the measured water permeability of stratum corneum; (ii) the particular lipid composition of the stratum corneum intercellular space; (iii) the absence of swelling of the stratum corneum intercellular lipid matrix upon hydration; and (iv) the simultaneous presence of hexagonal and orthorhombic hydrocarbon chain packing of the stratum corneum intercellular lipid matrix at physiologic temperatures. Further, the new model is consistent with skin barrier formation according to the membrane folding model of Norlén (2001). This new theoretical model could fully account for the extraordinary barrier capacity of mammalian skin and is hereafter referred to as the single gel phase model.

Journal of Investigative Dermatology

84158746

10.2307/1938063

Competition for Space, Disturbance, and the Structure of a Benthic Stream Community

Interspecific competition for space limits the distribution and abundance of many ben- thic insects on stones in a western Montana stream. The sessile caddisfly larva Leucotrichia pictipes is territorial and aggressively eliminates conspecifics and other species from its foraging territories. Territoriality produces an intraspecific pattern of regular spacing and negative spatial associations between Leucotrichia and several other sessile insects: Parargyractis confusalis, Rheotanytarsus sp. and Eukiefferiella sp. Experimental removals of Leucotrichia resulted in higher densities of other sessile species and several mobile insects, including Baetis, Glossosoma, and Simulium. These insects show broad microhabitat overlap with Leucotrichia; competition with Leucotrichia limits their dis- tributions and abundances within otherwise suitable microhabitats. Leucotrichia is the only species that monopolizes large areas of space. Physical disturbances interrupt the formation of competitive monopolies by Leucotrichia. During seasonal reduced flows, Leucotrichia is eliminated from stones and boulders in shallow water. Greater densities of a short-lived sessile species with multiple annual generations occupy this ephemeral spatial resource. On permanently submerged stones, Leucotrichia competitively affects a large part of the benthic fauna. On small stones that overturn with higher frequencies during flooding, Leucotrichia densities are reduced and species' abundances are highly equitable. Large, more stable substrates with greater densities of Leucotrichia are characterized by lower species evenness.

Ecology

84626390

10.1086/279724

On the Use of the Sucking-Fish for Catching Fish and Turtles: Studies in Echeneis or Remora, II

In 1507, there was published at Venice by Franconzio another collection of travels, entitled "Paesi Nouamente Retrouati Et Nous Mondo da Alberico Vesputio Florentino Intitulato" [Countries Newly Found and the New World of Albericus Vesputius Called the Florentine]. Chapters LXXXIIII to CXIIII faithfully reproduce the Libretto of 1504, are in fact a second edition of the Libretto, and need not detain us.14 All this however simply pushes the question back one step further and it now becomes "What or who is the source of Peter Martyr's information?" The answer is that these sources are identical with those for the "Life of Christopher Columbus " by his son Ferdinand, for Las Casas's history of the West Indies, and for Bernaldez's "Reyes Catalicos." In addition Dr. Eastman has skilfully worked out certain internal evidence which points directly to the one person who gave to Peter Martyr the data incorporated in Chapter XV of the Libretto. Let us first of all consider the account which Ferdinand gives of the fisherinan-fish incident, which seems to

The American Naturalist

42753798

10.1016/J.ADDR.2005.07.001

The basics and underlying mechanisms of mucoadhesion.

Mucoadhesion is where two surfaces, one of which is a mucous membrane, adhere to each other. This has been of interest in the pharmaceutical sciences in order to enhance localised drug delivery, or to deliver 'difficult' molecules (proteins and oligonucleotides) into the systemic circulation. Mucoadhesive materials are hydrophilic macromolecules containing numerous hydrogen bond forming groups, the carbomers and chitosans being two well-known examples. The mechanism by which mucoadhesion takes place has been said to have two stages, the contact (wetting) stage followed by the consolidation stage (the establishment of the adhesive interactions). The relative importance of each stage will depend on the individual application. For example, adsorption is a key stage if the dosage form cannot be applied directly to the mucosa of interest, while consolidation is important if the formulation is exposed to significant dislodging stresses. Adhesive joint failure will inevitably occur as a result of overhydration of a dosage form, or as a result of epithelia or mucus turnover. New mucoadhesive materials with optimal adhesive properties are now being developed, and these should enhance the potential applications of this technology.

Advanced Drug Delivery Reviews

137254443

10.1016/S1672-6529(09)60217-1

Anti-Erosion Function in Animals and its Biomimetic Application

Material failure is usually caused by corrosion, wear and mechanical damage. According to previous researches, erosion wear holds about 8% of regular wear in industrial production. In the present work, a new approach, which adopted the idea of coupling bionics to improve erosion resistance of machine parts, was presented. Simulation by ANSYS/LS-DYNA finite element software was applied to predict the relative erosion severity, and experiment optimum design theory was employed to design experiment scheme. Silica sand of particle size 105 µm–830 µm was used as the erodent. The erosion tests were carried out to validate the simulation results obtained. It is shown that the simulation results are in agreement with those of the experiment. The morphologies of eroded surface were examined by scanning electron microscope, and the possible wear mechanism was discussed.

Journal of Bionic Engineering

24336126

10.1098/RSPB.2010.0117

Bone density and the lightweight skeletons of birds

The skeletons of birds are universally described as lightweight as a result of selection for minimizing the energy required for flight. From a functional perspective, the weight (mass) of an animal relative to its lift-generating surfaces is a key determinant of the metabolic cost of flight. The evolution of birds has been characterized by many weight-saving adaptations that are reflected in bone shape, many of which strengthen and stiffen the skeleton. Although largely unstudied in birds, the material properties of bone tissue can also contribute to bone strength and stiffness. In this study, I calculated the density of the cranium, humerus and femur in passerine birds, rodents and bats by measuring bone mass and volume using helium displacement. I found that, on average, these bones are densest in birds, followed closely by bats. As bone density increases, so do bone stiffness and strength. Both of these optimization criteria are used in the design of strong and stiff, but lightweight, manmade airframes. By analogy, increased bone density in birds and bats may reflect adaptations for maximizing bone strength and stiffness while minimizing bone mass and volume. These data suggest that both bone shape and the material properties of bone tissue have played important roles in the evolution of flight. They also reconcile the conundrum of how bird skeletons can appear to be thin and delicate, yet contribute just as much to total body mass as do the skeletons of terrestrial mammals.

Proceedings of The Royal Society B: Biological Sciences

29745310

10.1111/J.1461-0248.2010.01537.X

Evidence for trans-generational medication in nature.

Parasites pose a serious threat to host fitness, and natural selection should favour host traits that reduce infection or disease symptoms. Here, we provide the first evidence of trans-generational medication, in which animals actively use medicine to mitigate disease in their offspring. We studied monarch butterflies and their virulent protozoan parasites, and found that neither caterpillars nor adult butterflies could cure themselves of disease. Instead, adult butterflies preferentially laid their eggs on toxic plants that reduced parasite growth and disease in their offspring caterpillars. It has often been suggested that sick animals may use medication to cure themselves of disease, but evidence for the use of medication in nature has so far been scarce. Our results provide evidence that infected animals may indeed use medicine as a defence against parasites, and that such medication may target an individual's offspring rather than the individual itself.

Ecology Letters

25331126

10.1038/NRMICRO2354

Bacterial polymers: biosynthesis, modifications and applications

Bacteria can synthesize a wide range of biopolymers that serve diverse biological functions and have material properties suitable for numerous industrial and medical applications. A better understanding of the fundamental processes involved in polymer biosynthesis and the regulation of these processes has created the foundation for metabolic- and protein-engineering approaches to improve economic-production efficiency and to produce tailor-made polymers with highly applicable material properties. Here, I summarize the key aspects of bacterial biopolymer production and highlight how a better understanding of polymer biosynthesis and material properties can lead to increased use of bacterial biopolymers as valuable renewable products.

Nature Reviews Microbiology

5836246

10.1242/JEB.02007

Water relations of tetrapod integument

SUMMARY The vertebrate integument represents an evolutionary compromise between the needs for mechanical protection and those of sensing the environment and regulating the exchange of materials and energy. Fibrous keratins evolved as a means of strengthening the integument while simultaneously providing a structural support for lipids, which comprise the principal barrier to cutaneous water efflux in terrestrial taxa. Whereas lipids are of fundamental importance to water barriers, the efficacy of these barriers depends in many cases on structural features that enhance or maintain the integrity of function. Amphibians are exceptional among tetrapods in having very little keratin and a thin stratum corneum. Thus, effective lipid barriers that are present in some specialized anurans living in xeric habitats are external to the epidermis, whereas lipid barriers of amniotes exist as a lipid-keratin complex within the stratum corneum. Amphibians prevent desiccation of the epidermis and underlying tissues either by evaporating water from a superficial aqueous film, which must be replenished, or by shielding the stratum corneum with superficial lipids. Water barrier function in vertebrates generally appears to be relatively fixed, although various species have `plasticity' to adjust the barrier effectiveness facultatively. While it is clear that both phenotypic plasticity and genetic adaptation can account for covariation between environment and skin resistance to water efflux, studies of the relative importance of these two phenomena are few. Fundamental mechanisms for adjusting the skin water barrier include changes in barrier thickness, composition and physicochemical properties of cutaneous lipids, and/or geometry of the barrier within the epidermis. While cutaneous lipids have been studied extensively in the contexts of disease and cosmetics, relatively little is known about the processes of permeability barrier ontogenesis related to adaptation and environment. Advances in such knowledge have didactic significance for understanding vertebrate evolution as well as practical application to clinical dermatology.

The Journal of Experimental Biology

10002324

10.1098/RSPB.2000.1153

The function of resilin in beetle wings

This account shows the distribution of elastic elements in hind wings in the scarabaeid Pachnoda marginata and coccinellid Coccinella septempunctata (both Coleoptera). Occurrence of resilin, a rubber–like protein, in some mobile joints together with data on wing unfolding and flight kinematics suggest that resilin in the beetle wing has multiple functions. First, the distribution pattern of resilin in the wing correlates with the particular folding pattern of the wing. Second, our data show that resilin occurs at the places where extra elasticity is needed, for example in wing folds, to prevent material damage during repeated folding and unfolding. Third, resilin provides the wing with elasticity in order to be deformable by aerodynamic forces. This may result in elastic energy storage in the wing.

Proceedings of The Royal Society B: Biological Sciences

6685435

10.1371/JOURNAL.PONE.0000132

A Predator from East Africa that Chooses Malaria Vectors as Preferred Prey

Background All vectors of human malaria, a disease responsible for more than one million deaths per year, are female mosquitoes from the genus Anopheles. Evarcha culicivora is an East African jumping spider (Salticidae) that feeds indirectly on vertebrate blood by selecting blood-carrying female mosquitoes as preferred prey. Methodology/Principal Findings By testing with motionless lures made from mounting dead insects in lifelike posture on cork discs, we show that E. culicivora selects Anopheles mosquitoes in preference to other mosquitoes and that this predator can identify Anopheles by static appearance alone. Tests using active (grooming) virtual mosquitoes rendered in 3-D animation show that Anopheles' characteristic resting posture is an important prey-choice cue for E. culicivora. Expression of the spider's preference for Anopheles varies with the spider's size, varies with its prior feeding condition and is independent of the spider gaining a blood meal. Conclusions/Significance This is the first experimental study to show that a predator of any type actively chooses Anopheles as preferred prey, suggesting that specialized predators having a role in the biological control of disease vectors is a realistic possibility.

PLOS ONE

84237835

10.1080/17088180809434786

Function of the Urnulae in Protecting the Red Velvet Mite, Balaustium Sp., Against Water Loss and in Enhancing its Activity at High Temperatures

Abstract Features of Balaustium sp. include resistance to intense heat and desiccation, affinity for hot surfaces in bright light, abundance in semi-arid/arid biotopes, and a large pair of secretory glands called umulae with no known function (defense secretion excepted). Here we show that the urnulae secrete a waterproofing barrier that reduces the mite's cuticular permeability to water. Exposure to white light was used to stimulate release of the secretion; the urnulae protruded and exuded streams of red fluid at the tip of this structure that covered the entire body. Results showed that mites coated with urnulae secretion lost water at approximately half the rate of mites that did not secrete. Similarly, urnulae secretion coated mites demonstrated an increase in water-tightness of the cuticle reflected by a 9°C elevation in temperature threshold for water loss on an evaporation curve, increasing their optimal temperature tolerance for survival (lethal permeability temperature, LPT). Results also show a 10 kJ/mol drop in activation energy (E a) for water loss, representative of a substantial cuticular modification, and a decrease in Arrhenius frequency steric factor A, indicating an overall decrease in body water losses. The absence of a critical transition temperature (CTT), however, reveals that urnulae secretion coating functions to resist a phase change as the temperature rises, permitting the mites to cope with high temperature without succumbing to water and heat stress, by inhibiting cuticular breakdown.

International Journal of Acarology

27010741

10.1105/TPC.109.069773

A Vacuolar Arsenite Transporter Necessary for Arsenic Tolerance in the Arsenic Hyperaccumulating Fern Pteris vittata Is Missing in Flowering Plants[W][OA]

Gametophytes of the fern Pteris vittata can accumulate and tolerate more than 1% of their dry weight as arsenic. The authors provide evidence that the ACR3 arsenic transporter protein plays an important role in tolerance to high levels of arsenic by transporting arsenic into the vacuole. The fern Pteris vittata tolerates and hyperaccumulates exceptionally high levels of the toxic metalloid arsenic, and this trait appears unique to the Pteridaceae. Once taken up by the root, arsenate is reduced to arsenite as it is transported to the lamina of the frond, where it is stored in cells as free arsenite. Here, we describe the isolation and characterization of two P. vittata genes, ACR3 and ACR3;1, which encode proteins similar to the ACR3 arsenite effluxer of yeast. Pv ACR3 is able to rescue the arsenic-sensitive phenotypes of yeast deficient for ACR3. ACR3 transcripts are upregulated by arsenic in sporophyte roots and gametophytes, tissues that directly contact soil, whereas ACR3;1 expression is unaffected by arsenic. Knocking down the expression of ACR3, but not ACR3;1, in the gametophyte results in an arsenite-sensitive phenotype, indicating that ACR3 plays a necessary role in arsenic tolerance in the gametophyte. We show that ACR3 localizes to the vacuolar membrane in gametophytes, indicating that it likely effluxes arsenite into the vacuole for sequestration. Whereas single-copy ACR3 genes are present in moss, lycophytes, other ferns, and gymnosperms, none are present in angiosperms. The duplication of ACR3 in P. vittata and the loss of ACR3 in angiosperms may explain arsenic tolerance in this unusual group of ferns while precluding the same trait in angiosperms.

The Plant Cell