75.5 Friday, Jan. 6 Evolution of elastic mechanisms in salamander tongues DEBAN, Stephen*; ANDERSON, Christopher; LARGHI, Nicholas; SANDUSKY, Paula; Univ. South Florida, Tampa firstname.lastname@example.org
Plethodontid salamanders are characterized by specialized tongue projection, with ballistic projection evolving three times independently. All ballistic taxa project their tongues with high muscle-mass specific power output (i.e., peak instantaneous mechanical power >1000 W/kg muscle mass) via an elastic-recoil mechanism that amplifies muscle power and confers relative thermal insensitivity to tongue projection. Using high-speed imaging and temperature manipulations, we probed the mechanism of tongue projection in several taxa with and without ballistic projection. We found that taxa with high power output (>1000 W/kg muscle mass) also posses low thermal sensitivity and vice versa, but that not all taxa with these features project their tongues ballistically. High power output and low thermal sensitivity may have evolved concomitantly twice in the Plethodontidae, in Hydromantes and in the clade containing Pseudotriton, Eurycea and Batrachoseps. Thermal sensitivity and low power output (<100 W/kg) were found in non-ballistic Plethodon and Desmognathus and are presumably ancestral for the family. These results suggest that both thermal insensitivity and high power output in excess of peak muscle power favor the evolution of elastic-recoil mechanisms, and may be a precursor to ballistic movement.