Meeting Abstract

17.1  Sunday, Jan. 4  Low thermal dependence of elastically-powered movement in salamanders DEBAN, S.M.; Univ. South Florida sdeban@cas.usf.edu

Biological springs in musculoskeletal systems provide a range of benefits to organisms including energy recovery, power amplification, improved force control, and expanded functional range of muscles. To test the hypothesis that, in addition, elastic recoil mechanisms extend the thermal range over which rapid, powerful movements can be performed in ectotherms, ballistic tongue projection was examined in plethodontid salamanders. Hydromantes platycephalus were imaged at 3-6 kHz feeding over a range of body temperatures and inverse dynamics analysis was performed on ballistic, elastically-powered tongue projection, and on non-ballistic, non-elastic (i.e. muscle-powered) tongue retraction. Temperature had no significant effect on projection distance or projection dynamics but strongly influenced retraction dynamics. Q₁₀ values over 5-20C were lower for dynamic parameters of elastic tongue projection than for those of non-elastic tongue retraction: peak velocity (1.2 for projection vs 1.4 for retraction), peak acceleration (1.2 vs 2.4), peak power (1.3 vs 3.5). These results reveal that tongue projection is less thermally dependent than retraction, and is consistent with the hypothesis that this lower thermal dependence may be due to the reliance of tongue projection on the elastic recoil of collagen fibers whose elastic properties are relatively thermally independent. Decoupling of the dynamics of muscle contraction, which generally have strong thermal dependence, from the dynamics of movement may be a general mechanism by which ectotherms can maintain high performance of predatory and escape behaviors at low temperatures.