Meeting Abstract
129.1 Monday, Jan. 7 Contrasting thermal effects on movements powered by elastic recoil and muscle contraction in chameleons living along a temperature gradient ANDERSON, C.V.*; TOLLEY, K.A.; University of South Florida, Tampa; South African National Biodiversity Institute, Cape Town cvanders@mail.usf.edu
Temperature has a strong effect on muscle contractile velocity, and thus movement performance, but elastically powered tongue projection in chameleons has been shown to be less thermally dependent than the associated muscle-powered retraction. Adaptation and acclimation to low muscle temperature are known to mitigate thermal effects in muscle-powered movements at low temperature, but natural selection might act differently on movements that benefit from lower thermal dependence (i.e., elastically powered movements). We hypothesize that between closely related chameleon taxa found along an environmental temperature gradient, performance of muscle-powered movements (tongue retraction) will be higher at lower temperatures for taxa found in colder environments than for taxa found in warmer environments. Conversely, performance of elastic recoil powered movements (tongue projection) will vary significantly less between the taxa. We imaged three taxa living along a strong elevation and temperature gradient in South Africa feeding at 15-35°C. We found that tongue projection performance for the taxa from the coldest environment was the most robust between 15 and 25°C (Q10 <1.04). Among the examined taxa, however, relative thermal effects on performance did not show altitudinal gradation, with the mid-elevation taxa maintaining the highest degree of performance for both tongue projection and retraction at 25°C. These results indicate that thermal effects on both elastic recoil and muscle-powered movements vary between species living in different thermal environments but that other environmental variables may aid in driving these performance curves.
