Variation in setal micromechanics and performance of two gecko species
- 292 Downloads
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.
KeywordsFrictional adhesion Work of detachment Effective elastic modulus Weibull distribution Toe detachment angle Template model
We thank four previous anonymous reviewers, Craig McGowan, Mitch Day, Chloe Stenkamp-Strahm, the Harmon, Rosenblum, and Autumn labs for helpful advice and comments, Matt Wilkinson for assistance with laboratory equipment, Katie Pond and Christine Van Tubbe for help with animal care, Meghan Wagner and Andrew Schnell for assistance in the laboratory, and the University of Idaho IACUC for approval of the project (Protocol #2010-40). Aaron Bauer and Todd Jackman also provided assistance and support. We thank the University of Idaho and the National Science Foundation (DEB-0844523, IOS-0847953 and NBM-0900723) for funding.
- Gamble T, Greenbaum E, Jackman TR, Russell AP, Bauer AM (2012) Repeated origin and loss of adhesive toepads in geckos. PLoS ONE 7(6):e39429. doi: 10.1371/journal.pone.0039429
- Glaw F, Vences M (2007) A field guide to the amphibians and reptiles of Madagascar. 3rd edn. Köln, Vences & Glaw, Köln, GermanyGoogle Scholar
- Glossip D, Losos JB (1997) Ecological correlates of number of subdigital lamellae in anoles. Herpetologica 53(2):192–199Google Scholar
- Hagey TJ (2013) Mechanics, diversity, and ecology of Gecko adhesion. University of Idaho, MoscowGoogle Scholar
- Losos JB (2009) Lizards in an evolutionary tree: the ecology of adaptive radiation in anoles. University of California Press, BerkeleyGoogle Scholar
- Peattie AM (2007) The function and evolution of Gekkotan adhesive feet. Doctor of Philosophy, University of California, BerkeleyGoogle Scholar
- Rosler H, Bauer AM, Heinicke MP, Greenbaum E, Jackman T, Nguyen TQ, Ziegler T (2011) Phylogeny, taxonomy, and zoogeography of the genus Gekko Laurenti, 1768 with the revalidation of G. reevesii Gray, 1831 (Sauria: Gekkonidae). Zootaxa 2989:1–50Google Scholar
- Russell AP (1977) Genera Rhoptropus and Phelsuma (Reptilia Gekkonidae) in Southern-Africa—case of convergence and a reconsideration of biogeography of Phelsuma. Zool Afr 12(2):393–408Google Scholar