Peeling behavior of a bio-inspired nano-film on a substrate

A peeling model is proposed to analyze the peeling properties of bio-mimetic nano-films using the finite element method (FEM) and theoretical approach. The influences of the nano-film's adhesion length, thickness, elastic modulus, roughness and peeling angle on the peeling force were considered as well as the effect of the viscoelastic behavior. It has been found that the effective adhesion length, at which the peeling force attained maximum, was much smaller than the real length of nano-films; and the shear force dominated in the case of smaller peeling angles, whereas, the normal force dominated at larger peeling angles. The total peeling force decreased with an increasing peeling angle. Two limiting values of the peeling-off force can be found in the viscoelastic model, which corresponds to the smaller and larger loading rate cases. The effects of nano-film thickness and Young's modulus on peeling behaviors were also discussed. The results obtained are helpful for understanding the micro-adhesion mechanisms of biological systems, such as geckos. (C) 2010 Elsevier Ltd. All rights reserved.

Jettisoning Ballast or Fuel? Caudal Autotomy and Locomotory Energetics of the Cape Dwarf Gecko Lygodactylus capensis (Gekkonidae)

Many lizard species will shed their tail as a defensive response (e.g., to escape a putative predator or aggressive conspecific). This caudal autotomy incurs a number of costs as a result of loss of the tail itself, loss of resources (i.e., stored in the tail or due to the cost of regeneration), and altered behavior. Few studies have examined the metabolic costs of caudal autotomy. A previous study demonstrated that geckos can move faster after tail loss as a result of reduced weight or friction with the substrate; however, there are no data for the effects of caudal autotomy on locomotory energetics. We examined the effect of tail loss on locomotory costs in the Cape dwarf gecko Lygodactylus capensis (similar to 0.9 g) using a novel method for collecting data on small lizards, a method previously used for arthropods. We measured CO2 production during 5-10 min of exhaustive exercise (in response to stimulus) and during a 45-min recovery period. During exercise, we measured speed (for each meter moved) as well as total distance traveled. Contrary to our expectations, tailless geckos overall expended less effort in escape running, moving both slower and for a shorter distance, compared with when they were intact. Tailless geckos also exhibited lower excess CO2 production (CO2 production in excess of normal resting metabolic rate) during exercising. This may be due to reduced metabolically active tissue (tails represent 8.7% of their initial body mass). An alternative suggestion is that a change in energy substrate use may take place after tail loss. This is an intriguing finding that warrants future biochemical investigation before we can predict the relative costs of tail loss that lizards might experience under natural conditions.

Agriculture modifies the seasonal decline of breeding success in a tropical wild bird population

1.Habitat conversion for agriculture is a major driver of biodiversity loss, but our understanding of the demographic processes involved remains poor. We typically investigate the impacts of agriculture in isolation even though populations are likely to experience multiple, concurrent changes in the environment (e.g. land and climate change). Drivers of environmental change may interact to affect demography but the mechanisms have yet to be explored fully in wild populations. 2.Here, we investigate the mechanisms linking agricultural land-use with breeding success using long-term data for the formerly Critically Endangered Mauritius kestrel Falco punctatus; a tropical forest specialist that also occupies agricultural habitats. We specifically focused on the relationship between breeding success, agriculture and the timing of breeding because the latter is sensitive to changes in climatic conditions (spring rainfall), and enables us to explore the interactive effects of different (land and climate) drivers of environmental change. 3.Breeding success, measured as egg survival to fledging, declines seasonally in this population, but we found that the rate of this decline became increasingly rapid as the area of agriculture around a nest site increased. If the relationship between breeding success and agriculture was used in isolation to estimate the demographic impact of agriculture it would significantly under-estimate breeding success in dry (early) springs, and over-estimate breeding success in wet (late) springs. 4.Analysis of prey delivered to nests suggests that the relationship between breeding success and agriculture might be due, in part, to spatial variation in the availability of native, arboreal geckos. 5.Synthesis and applications. Agriculture modifies the seasonal decline in breeding success in this population. As springs are becoming wetter in our study area and since the kestrels breed later in wetter springs, the impact of agriculture on breeding success will become worse over time. Our results suggest that forest restoration designed to reduce the detrimental impacts of agriculture on breeding may also help reduce the detrimental effects of breeding late due to wetter springs. Our results therefore highlight the importance of considering the interactive effects of environmental change when managing wild populations.

A new species of lizard genus Gymnodactylus Spix, 1825 (Squamata: Gekkota: Phyllodactylidae) from Serra do Sincora, northeastern Brazil, and the status of G. carvalhoi Vanzolini, 2005

A new species of gekkonid lizard genus Gymnodactylus Spix, 1825 is described on the basis of material collected in the ""campos rupestres"" (open rocky communities) of Mucuge municipality, northeastern Brazil. G. vanzolinii sp. nov. differs from its congeners in the number of transverse and longitudinal rows of dorsal tubercles and color pattern. It is thought to be closer to G. guttulatus which also occurs and is restricted to the rocky communities from highland open areas in the Espinhaco mountain range. The discovery leads to a reevaluation of the taxonomic status of G. carvalhoi Vanzolini, 2005, which is here considered a synonym of G. amarali Barbour, 1925.

Chromosomal evolution in Gekkonidae. I. Chromosome painting between Gekko and Hemidactylus species reveals phylogenetic relationships within the group

Geckos are a large group of lizards characterized by a rich variety of species, different modes of sex determination and diverse karyotypes. In spite of many unresolved questions on lizards' phylogeny and taxonomy, the karyotypes of most geckos have been studied by conventional cytogenetic methods only. We used flow-sorted chromosome-specific painting probes of Japanese gecko (Gekko japonicus), Mediterranean house gecko (Hemidactylus turcicus) and flat-tailed house gecko (Hemidactylus platyurus) to reveal homologous regions and to study karyotype evolution in seven gecko species (Gekko gecko, G. japonicus, G. ulikovskii, G. vittatus, Hemidactylus frenatus, H. platyurus and H. turcicus). Generally, the karyotypes of geckos were found to be conserved, but we revealed some characteristic rearrangements including both fissions and fusions in Hemidactylus. The karyotype of H. platyurus contained a heteromorphic pair in all female individuals, where one of the homologues had a terminal DAPI-negative and C-positive heterochromatic block that might indicate a putative sex chromosome. Among two male individuals studied, only one carried such a polymorphism, and the second one had none, suggesting a possible ZZ/ZW sex determination in some populations of this species. We found that all Gekko species have retained the putative ancestral karyotype, whilst the fission of the largest ancestral chromosome occurred in the ancestor of modern Hemidactylus species. Three common fissions occurred in the ancestor of Mediterranean house and flat-tailed house geckos, suggesting their sister group relationships. PCR-assisted mapping on flow-sorted chromosome libraries with conserved DMRT1 gene primers in G. japonicus indicates the localization of DMRT1 gene on chromosome 6.

Six species of Amazonian Woodcreepers (Aves: Dendrocolaptidae) preying upon lizards and frogs

Dietary data from a large sample of woodcreepers (16 spp., n?=?139), revealed that six species of dendrocolaptids occasionally feed upon lizards and frogs. These birds, which are mainly insectivorous, encounter and feed on lizards while perching on tree trunks, probably in association with army-ant swarm feeding behaviour. Frog intake may be related to declines in the abundance of invertebrate prey. The bones recovered were identified as one small species of gecko, Gonatodes humeralis, and at least one anuran. We estimate that in the entire sample, about eight lizards and two frogs were ingested. The partially digested gecko material allows determination of which bones are more resistant to digestion, although it is possible that these elements were differentially retained in the stomach. These elements correspond to the more frequently preserved bones in the fossil record of geckos, indicating that the same portions of the skeleton persist under the processes of both digestion and fossilization.

Wet bioadhesion in tree frogs

Viele Tiere wie etwa Geckos oder Laubfrösche können mittels ihrer Haftscheiben an Oberflächen kleben. Diese Haftscheiben ermöglichen es den Tieren, sich während ihrerrnFortbewegung an Oberflächen anzuheften und wieder zu lösen unabhängig von denrnvorherrschenden Umweltbedingungen. Frösche besitzen mikro- und nanostrukturierternsowie charakteristisch geformte Haftscheiben an Finger- und Zehenenden. Ihre besonderernevolutionäre Errungenschaft, sich stark und zugleich reversibel in sowohl trockenen alsrnauch feuchten Umgebungen anzuhaften, hat die Wissenschaft zur Nachahmung und Untersuchungrndieser Strukturen inspiriert. Zum besseren Verständnis der Mechanismen vonrnAnhaftung und Loslösung bei Laubfröschen wurden weiche, elastische und mikrostrukturierternOberflächen hergestellt, indem PDMS (Polydimethylsiloxan) auf einer Siliziummaskernmit Hexagonstruktur aufgetragen und vernetzt wurde. Dadurch wurden Anordnungenrnvon hexagonalen Mikrosäulen mit spezifischen geometrischen Eigenschaften undrnunterschiedlichen Kontaktgeometrien (normale, flache Form, T-Form und konkave Formrnder Säulenenden) erhalten. Um den Einfluss der van-der-Waals, hydrodynamischen,rnKapillar-und Adhäsionskräfte zu verstehen, wurden verschiedene experimentelle Ansätzernverfolgt: Die auf eine einzelne Säule wirkenden Adhäsionskräfte wurden mittelsrnRasterkraftmikroskopie gemessen. Dazu wurden speziell hergestellte kolloidale Sensorenrnverwendet. Diese Experimente wurden sowohl mit als auch ohne Flüssigkeitsfilm auf derrnSäule durchgeführt. Die Ergebnisse zeigten den Beitrag von Kapillarkraft und direktenrnKontaktkräften zur Adhäsionskraft bei Vorliegen eines Flüssigkeitsfilms. Die Adhäsionrnfiel umso größer aus, je weniger Flüssigkeit zwischen Sensor und Säule vorhanden war.rnIm Falle einer trockenen Adhäsion zeigte die Säule mit T-Form die höchste Adhäsion. Darndie Haftscheiben der Laubfrösche weich sind, können sie dynamisch ihre Form ändern,rnwas zu einer Änderung der hydrodynamischen Kraft zwischen Scheibe und Oberflächernführt. Der Einfluss der Oberflächenverformbarkeit auf die hydrodynamische Kraft wurderndaher am Modellsystem einer Kugel untersucht, welche sich einer weichen und ebenenrnOberfläche annähert. Dieses System wurde sowohl theoretisch über die Simulation finiterrnElemente als auch experimentell über die Messung mit kolloidalen Sonden untersucht.rnSowohl experimentelle Ergebnisse als auch die Simulationen ergaben eine Abnahme derrnhydrodynamischen Kraft bei Annäherung des kolloidalen Sensors an eine weiche undrnelastische Oberfläche. Beim Entfernen der Sensors von der Oberfläche verstärkte sichrndie hydrodynamische Anziehungskraft. Die Kraft, die zur Trennung eines Partikels von einer Oberfläche in Flüssigkeit notwendig ist, ist für weiche und elastischen Oberflächenrngrößer als für harte Oberflächen. In Bezug zur Bioadhäsion bei Laubfröschen konnternfestgestellt somit festgestellt werden, dass sich der hydrodynamische Anteil zur feuchtenrnBioadhäsion aufgrund der weichen Oberfläche erhöht. Weiterhin wurde der Einflussrndes Aspektverhältnisses der Säulen auf die Reibungskraft mittels eines kolloidalen Sensorsrnuntersucht. Gestreckte Säulen zeigten dabei eine höhere Reibung im Vergleich zu.rnSäulen mit einem gestreckten Hexagon als Querschnitt.

Sphaerodactylus / by Thomas Barbour.

v.47:no.3 (1921)

Geographic parthenogenesis in the Australian arid zone: I. A climatic analysis of the Heteronotia binoei complex (Gekkonidae)

Patterns of geographic parthenogenesis can provide insight into the ecological implications of the transition from sexual to parthenogenetic reproduction. We analysed quantitatively the environmental niches occupied by sexual and parthenogenetic geckos of the Heteronotia binoei complex in the Australian and zone. This complex consists of two independently derived maternal lineages of hybrid parthenogens, which, in turn, include two different triploid races that resulted from reciprocal backcrossing with the parental sexual taxa. The sexual progenitors are still extant and occupy very distinct environmental niches. The triploid parthenogenetic races are biased in their environmental niche towards those of the sexual races for which their genomes are biased and this dosage effect is apparent in both maternal lineages. Thus triploidy may have benefited the parthenogens through partial recovery of the parental niches. Although the parthenogens have a broader geographic distribution than their sexual progenitors, their environmental niche is narrower and biased towards one of the sexual races. In keeping with general patterns of geographic parthenogenesis. parthenogenetic H. binoei occupy a harsher environment than the sexual forms. occurring in regions of persistently low rainfall. Bioclimatic modelling suggests patterns of rainfall are important in limiting the distribution of sexual and parthenogenetic taxa. and extrapolation from the current bioclimatic profiles indicates potential for further eastward range expansion by the parthenogens.

The importance of marine subsidies for terrestrial consumers in coastal Peru

The Peruvian coast is one the best examples of cross-ecosystem food web exchanges, in which resources from one of the richest marine ecosystems subsidize consumers in one of the driest deserts on Earth. Marine subsidies are resources that originate in the marine ecosystem, and that contribute to increase the density of consumers in the recipient ecosystem. I examined the effects of marine subsidies on animal populations in the Peruvian coastal desert. ^ I combined several approaches to study the linkages between marine resources and terrestrial consumers, such as surveying the spatial distribution and estimating the relative abundance of terrestrial consumers, studying the diet of geckos and lizards through stomach content analyses, and examining the desert food web with carbon and nitrogen stable isotope analyses. ^ I found that the distribution and diet of desert consumers were tightly coupled to the availability of marine subsidies. I revealed linkages along two pathways of nutrient fluxes: tidal action that washes ashore macroalgae and cadavers of marine organisms, and animal transport in places where pinnipeds and seabirds congregate for reproduction. In the first pathway, intertidal algivivores made marine resources available to terrestrial consumers by moving between the intertidal and supratidal zone. The relative contribution of terrestrial and algal carbon sources varied among terrestrial consumers, because scorpions assimilated a lower proportion of energy from macroalgae than did geckos and solifuges. In the second pathway, I found that pinniped colonies influenced the diet of desert consumers, and contributed to support large populations of lizards and geckos. By combining field observations, and stomach and stable isotope analyses, I constructed a simplified food web for a large sea lion colony, showing the number of trophic levels that originate from pinniped-derived nutrients. ^ My study demonstrates the enormous importance of marine resources for the diet of desert consumers. The near absence of rainfall along the Peruvian coast promotes an extreme dependence of terrestrial consumers on marine resources, and causes permanent food web effects that are affected by temporal variability in marine productivity, rather then temporal patterns of desert plant growth. ^

The importance of marine subsidies for terrestrial consumers in coastal Peru

The Peruvian coast is one the best examples of cross-ecosystem food web exchanges, in which resources from one of the richest marine ecosystems subsidize consumers in one of the driest deserts on Earth. Marine subsidies are resources that originate in the marine ecosystem, and that contribute to increase the density of consumers in the recipient ecosystem. I examined the effects of marine subsidies on animal populations in the Peruvian coastal desert. I combined several approaches to study the linkages between marine resources and terrestrial consumers, such as surveying the spatial distribution and estimating the relative abundance of terrestrial consumers, studying the diet of geckos and lizards through stomach content analyses, and examining the desert food web with carbon and nitrogen stable isotope analyses. I found that the distribution and diet of desert consumers were tightly coupled to the availability of marine subsidies. I revealed linkages along two pathways of nutrient fluxes: tidal action that washes ashore macroalgae and cadavers of marine organisms, and animal transport in places where pinnipeds and seabirds congregate for reproduction. In the first pathway, intertidal algivivores made marine resources available to terrestrial consumers by moving between the intertidal and supratidal zone. The relative contribution of terrestrial and algal carbon sources varied among terrestrial consumers, because scorpions assimilated a lower proportion of energy from macroalgae than did geckos and solifuges. In the second pathway, I found that pinniped colonies influenced the diet of desert consumers, and contributed to support large populations of lizards and geckos. By combining field observations, and stomach and stable isotope analyses, I constructed a simplified food web for a large sea lion colony, showing the number of trophic levels that originate from pinniped-derived nutrients. My study demonstrates the enormous importance of marine resources for the diet of desert consumers. The near absence of rainfall along the Peruvian coast promotes an extreme dependence of terrestrial consumers on marine resources, and causes permanent food web effects that are affected by temporal variability in marine productivity, rather then temporal patterns of desert plant growth.

The taxonomy, zoogeography and ecology of amphibians and reptiles of Hin Nam No National Protected Area (Laos) in comparison with data from Phong Nha – Ke Bang National Park (Vietnam).

In this thesis the mostly unknown herpetofauna in Hin Nam No National Protected Area Laos in the northern Truong Son Range was for the first time intensively investigated, and its diversity was compared to the bordering, and well-investigated Phong Nha - Ke Bang National Park in Vietnam. Twelve new vertebrate species were described comprising 11 geckonids (Cyrtodactylus bansocensis, C. calamei, C. hinnamnoensis, C. jaegeri, C. rufford, C. sommerladi, C. soudthichaki, Gekko boehmei, G. bonkowskii, G. sengchanthavongi, G. thakhekensis, Lycodon banksi and one colubrid snake (Lycodon banksi). Seven species were discovered for the first time in Laos including three frogs (Gracixalus quyeti, G. supercornutus, Rhacophorus maximus), two geckos (Cyrtodactylus cryptus, C. pseudoquadrivirgatus) and two snakes (Lycodon futsingensis, L. ruhstrati abditus). The main hypothesis that the Truong Son Range acted as a biogeographic barrier for the distribution of amphibians and reptiles could be confirmed at least for karst adapted gekkonids. Compared to other herpetofaunal groups the number of gekkonids in karst formations was particularly high (seven bent-toed geckos, four true geckos). By comparing the relative amounts of shared species in Hin Nam No and Phong Nha - Ke Bang, it is interesting to note that fewer reptile species (38%) than amphibian species (66%) were shared between both regions. This might indicate that the Truong Son Range acts as a stronger biogeographical barrier for reptiles than for amphibians. Two pairs of karst-adapted cryptic gecko species (i.e. species with distinct genetic differences, but a similar phenotype) occurred on both sides of the Truong Son Range. Only in one case these were sibling species (Crytodactylus sommerladi in Laos versus C. roesleri in Vietnam), but not in the other (C. hinnamnoensis in Laos versus C. phongnhakebangensis in Vietnam). On the Laotian side, nine gecko species (Cyrtodactylus bansocensis, C. calamei, C. darevskii, C. hinnamnoensis, C. khammouanensis, C. multiporus, C. sommerladi, G. boehmei, G. sengchanthavongi) currently have to be regarded as endemic to the Hin Nam No region. On the Vietnamese side, seven species including two bent-toed geckos (Cyrtodactylus phongnhakebangensis and C. roesleri), three skinks (Lygosoma boehmei, Sphenomorphus tetradactylus and Tropidophorus noggei), and two snakes (Hebius andreae and Boiga bourreti) are currently only known from Phong Nha - Ke Bang and adjacent regions. These high numbers of potential endemic species together with the cryptic species complex in Cyrtodactylus provide strong evidence that the karst formations in the northern Truong Son Range represent a hot spot of reptile diversity and of speciation in Crytodactylus in particular. Correct species identification is a fundamental requirement for conservation measures. The discovery of cryptic species complexes poses a challenge for alpha taxonomy and species conservation, because the true distribution ranges of the species are in fact much smaller than previously assumed. Species conservation in this area of Laos is facing a number of further problems. New and potentially endemic species were discovered in highly populated and disturbed areas. Conversion of the Ho Chi Minh Trail into a highway provided easy access for farmers and still continues to accelerate the destruction of remote forest areas. Southern Hin Nam No with its high diversity of endemic species was identified as the first priority area for conservation. Also Ban Soc, an area isolated from Hin Nam No, should be among the conservation priorities because this region houses a so far overlooked population of the critically endangered Siamese crocodile. Efforts to establish a legal conservation status for this habitat are in progress.