Stick or grip? Co-evolution of adhesive toepads and claws in Anolis lizards

Exploring the relationship between phenotype and performance in an ecological and evolutionary context is crucial to understand the adaptive nature of phenotypic traits. Despite their ubiquity in vertebrates, few studies have examined the functional and ecological significance of claw morphologies. Here we examine the adhesive toepad and claw system of Anolis lizards. Claw characters are significantly different between lizards classified as arboreal (perch height > 1 m)and non-­‐arboreal (perch height < 1 m). Arboreal species possess significantly higher and longer claws, and show trends toward decreased claw curvature and wider claw tip angles. Toepad size and claw length and height are tightly correlated with each other and with perch height, suggesting that the adhesive toepad and gripping claw have co-­‐evolved to accommodate different habitats. The functional morphology and evolution of claws are ripe areas for future investigation.Organismic and Evolutionary Biolog

Sampling theory for not necessarily band-limited functions. An historical overview

SIGLETIB Hannover: RN 2414(377) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Frictional and elastic energy in gecko adhesive detachment

Geckos use millions of adhesive setae on their toes to climb vertical surfaces at speeds of over 1 m s−1. Climbing presents a significant challenge for an adhesive since it requires both strong attachment and easy, rapid removal. Conventional pressure-sensitive adhesives are either strong and difficult to remove (e.g. duct tape) or weak and easy to remove (e.g. sticky notes). We discovered that the energy required to detach adhering tokay gecko setae (Wd) is modulated by the angle (θ) of a linear path of detachment. Gecko setae resist detachment when dragged towards the animal during detachment (θ=30°) requiring Wd=5.0±0.86 (s.e.) J m−2 to detach, largely due to frictional losses. This external frictional loss is analogous to viscous internal frictional losses during detachment of pressure-sensitive adhesives. We found that, remarkably, setae possess a built-in release mechanism. Setae acted as springs when loaded in tension during attachment and returned elastic energy when detached along the optimal path (θ=130°), resulting in Wd=−0.8±0.12 J m−2. The release of elastic energy from the setal shaft probably causes spontaneous release, suggesting that curved shafts may enable easy detachment in natural, and synthetic, gecko adhesives

2010-06-15

2010-06-1

Variation in Setal Micromechanics and Performance of Two Gecko Species

Biomechanical models of the gecko adhesive system typically focus on setal mechanics from a single gecko species, Gekko gecko. In this study, we compared the predictions from three mathematical models to experimental observations considering an additional gecko species Phelsuma grandis, to quantify interspecific variation in setal micromechanics. We also considered the accuracy of our three focal models: the frictional adhesion model, work of detachment model, and the effective modulus model. Lastly, we report a novel approach to quantity the angle of toe detachment using the Weibull distribution. Our results suggested the coupling of frictional and adhesive forces in isolated setal arrays first observed in G. gecko is also present in P. grandis although P. grandis displayed a higher toe detachment angle, suggesting they produce more adhesion relative to friction than G. gecko. We also found the angle of toe detachment accurately predicts a species’ maximum performance limit when fit to a Weibull distribution. When considering the energy stored during setal attachment, we observed less work to remove P. grandis arrays when compared to G. gecko, suggesting P. grandis arrays may store less energy during attachment, a conclusion supported by our model estimates of stored elastic energy. Our predictions of the effective elastic modulus model suggested P. grandis arrays to have a lower modulus, Eeff, but our experimental assays did not show differences in moduli between the species. The considered mathematical models successfully estimated most of our experimentally measured performance values, validating our three focal models as template models of gecko adhesion (see Full and Koditschek 1999), and suggesting common setal mechanics for our focal species and possibly for all fibular adhesives. Future anchored models, built upon the above templates, may more accurately predict performance by incorporating additional parameters, such as variation in setal length and diameter. Variation in adhesive performance may affect gecko locomotion and as a result, future ecological observations will help to determine how 31 species with different performance capabilities use their habitat

Data from: Variation in setal micromechanics and performance of two gecko

Biomechanical models of the gecko adhesive system typically focus on setal mechanics from a single gecko species, Gekko gecko. In this study, we compared the predictions from three mathematical models with experimental observations considering an additional gecko species Phelsuma grandis, to quantify interspecific variation in setal micromechanics. We also considered the accuracy of our three focal models: the frictional adhesion model, work of detachment model, and the effective modulus model. Lastly, we report a novel approach to quantify the angle of toe detachment using the Weibull distribution. Our results suggested the coupling of frictional and adhesive forces in isolated setal arrays, first observed in G. gecko is also present in P. grandis although P. grandis displayed a higher toe detachment angle, suggesting they produce more adhesion relative to friction than G. gecko. We also found the angle of toe detachment accurately predicts a species’ maximum performance limit when fit to a Weibull distribution. When considering the energy stored during setal attachment, we observed less work to remove P. grandis arrays when compared with G. gecko, suggesting P. grandis arrays may store less energy during attachment, a conclusion supported by our model estimates of stored elastic energy. Our predictions of the effective elastic modulus model suggested P. grandis arrays to have a lower modulus, E eff, but our experimental assays did not show differences in moduli between the species. The considered mathematical models successfully estimated most of our experimentally measured performance values, validating our three focal models as template models of gecko adhesion (see Full and Koditschek in J Exp Biol 202(23):3325–3332, 1999), and suggesting common setal mechanics for our focal species and possibly for all fibular adhesives. Future anchored models, built upon the above templates, may more accurately predict performance by incorporating additional parameters, such as variation in setal length and diameter. Variation in adhesive performance may affect gecko locomotion and as a result, future ecological observations will help to determine how species with different performance capabilities use their habitat

toe detachment angle trials

Our observed measurements of toe pad performance (toe detachment angle). These data include all of our observed trials, covering multiple individuals. The "individual" column represents the "names" of the individual animals tested and span multiple studies, hence there is no universal naming theme. Unique names relate to each individual. Note that some Anolis species are assigned a name of "NA" indicating that individual was not recored for that species. Following Hagey it al Journal of Experimental Biology 2016 219: 1603-1607; doi: 10.1242/jeb.129940, we fit each individual's set of trials to the weibull distribution, estimating a scale parameter with error for each individual. We then calculated a weighted species average using each individuals estimated scale parameter, weighted by the inverse of their error