GARTNER, G.E.A.*; O’REILLY, J.C.; University of Miami, Florida; University of Miami, Florida: Are caeciliid caecilians (Amphibia: Gymnophiona) superior burrowers?

Caecilians are limbless, burrowing amphibians that are found throughout most of the humid tropics. Previous studies have concluded that there is a general trend among caecilians towards a more fossorial lifestyle that is reflected in morphological specializations that include a more sub-terminal mouth opening and a reduction in the number of bones in the skull. In this scheme, ichthyophiids represent the generalized condition, while caeciliids are considered derived. Ducey et. al. (1993) tested the putative burrowing superiority of caeciliids and found conflicting results. Of the caeciliids tested (Dermophis, Gymnopis and Schistometopum), only Dermophis was willing to initiate burrowing in more compact soil than Ichthyophis. We approached this hypothesis from a biomechanical standpoint and quantified the force exerted during burrowing in Dermophis and Ichthyophis. We induced them to crawl within an acrylic channel and push against a static vertical block affixed to a force plate. Maximum pushing force increases with increasing body cross-section in Dermophis. However, there is no difference in maximum force production between Dermophis and Ichthyophis of similar body cross-section. We conclude that there is no evidence for superior burrowing performance in caeciliids. The results of Ducey et al. were most likely due to the fact the Dermophis they used were much larger, on average, than the other species included in their study.