75.4 Friday, Jan. 6 Thermal effects on the performance, motor control, and muscle dynamics of tongue projection in a plethodontid salamander ANDERSON, Christopher V.*; LARGHI, Nicholas P.; CREEMERS, Shelby; DEBAN, Stephen M.; University of South Florida, Tampa firstname.lastname@example.org
Temperature has a strong effect on muscle contractile velocity and thus movement performance. Elastically powered tongue projection of Chamaeleo, Bufo and Hydromantes have been shown to be less thermally dependent than their associated muscle-powered retraction. We hypothesize that the low thermal sensitivity of elastically powered ballistic tongue projection is generalized to other ballistic movements and that the low thermal sensitivity of tongue projection occurs despite profound effects of temperature on muscle dynamics and motor control, due to rapid elastic recoil. We examined the thermal effects on kinematics, motor control, and muscle dynamics associated with both tongue projection and retraction in a plethodontid salamander with a convergent ballistic tongue projection mechanism, Eurycea guttolineata. Specimens were imaged feeding at 5-25°C, while simultaneously recording electromyographic activity of the tongue projector (SAR) and retractor (RCP) muscles. We examined the muscle dynamics of both muscles across the same thermal range. We found that elastically powered tongue projection maintains a significantly higher degree of performance at low temperature than retraction, which experiences a significant performance loss with decreasing temperature and has higher Q10 values than projection. Similarly, muscle activity durations and latencies show a 5-25°C Q10 >1.4 for both the SAR and RCP muscles. Further, contraction of the SAR muscle showed a larger effect of temperature on dynamic properties than on static properties. These results fail to support the alternative hypothesis that Eurycea maintain tongue projection performance by maintaining muscle contractile rate performance at low temperature and support the generality of low thermal sensitivity in ballistic movements utilizing elastic recoil.