Meeting Abstract

P2.127  Saturday, Jan. 5  Functional morphology of the smallest ballistic tongue ISRAEL, S.*; DEBAN, S.M.; Univ. of South Florida, Tampa; Univ. of South Florida, Tampa segalli@mail.usf.edu

An elastic-recoil mechanism in the tongue-projection system has evolved independently in three lineages of plethodontid salamanders. This mechanism increases performance and provides thermal insensitivity to projection, allowing an advantage over muscle-powered movements at lower temperatures. We hypothesized, based on its morphology and phylogenetic relationships, that the miniaturized bolitoglossine Thorius—one of the smallest vertebrates—uses an elastic tongue-projection mechanism like other bolitoglossines (e.g., Bolitoglossa). We asked if its small adult size (~20 mm SVL) limits its ability to modulate its tongue movements as do other plethodontids or has other performance consequences. Morphological examination revealed a reduced number of myofibers in its tongue muscles (e.g., 6-8 fibers in the retractor muscle), and unusual folding of the hyobranchial apparatus. High-speed imaging (15 kHz) and inverse-dynamics analysis of the tongue projection and retraction movements revealed that tongue projection in Thorius is ballistic and elastically-powered, and shows low thermal dependence (Q₁₀ of peak velocity <1.5), while retraction is muscle powered and non-elastic. Thorius modulates its tongue movements in response to prey distance and appears to suffer no significant performance consequences of its reduced body size.