Meeting Abstract

17.4  Sunday, Jan. 4  Chameleons Maintain High-Performance Tongue Projection at Low Temperature ANDERSON, C.V.*; DEBAN, S.M.; University of South Florida; University of South Florida cvanders@mail.usf.edu

The impact of environmental factors on the physiology of ectotherms such as lizards, for example, the effect of temperature on muscle contraction velocity, are known to constrain natural activity patterns. Low temperatures are expected to impact performance of muscle-powered movements such as locomotion and tongue protraction and thereby hinder the ability of many lizards to capture prey. Chameleons are unusual among lizards in that they do not pursue prey by chasing and lunging, but instead use ballistic tongue projection to ambush prey. We hypothesize that chameleons are able to maintain tongue projection performance at a high level at low temperatures-despite the strong influence of temperature on muscle dynamics-by virtue of their tongue projection mechanism, which has been shown to use rapid recoil of elastic collagenous sheaths within the tongue to power tongue launch. We further hypothesize that tongue retraction performance, which relies on the retractor muscle doing work directly on the tongue and prey, is affected strongly by temperature. To test our hypotheses, we imaged Chamaeleo calyptratus at 3000 Hz feeding on crickets at 15-35C. For each feeding event, we calculated instantaneous velocity, acceleration and power of the tongue and calculated Q₁₀ values of these parameters for both projection and retraction. In accord with our hypothesis, C. calyptratus is able to maintain tongue projection performance over the examined temperature range and that peak mass specific power of elastically powered projection is far less sensitive to temperature (Q₁₀=1.21) than muscle-powered retraction (Q₁₀=3.67). The relative temperature insensitivity of tongue projection, combined with the ambush hunting strategy of chameleons, may ease temperature limitations on their activity patterns and may explain observations of chameleon activity over a wider temperature range than sympatric lizard species.