Meeting Abstract

32.1  Wednesday, Jan. 5  Temperature insensitivity of prey-capture dynamics in Rana pipiens reveals an elastic recoil mechanism SANDUSKY, P.E.*; DEBAN, S.M.; University of South Florida, Tampa; University of South Florida, Tampa psandusky@mail.usf.edu

In ectotherms, thermal independence in the kinematics and dynamics of a movement suggests that an underlying physical mechanism, such as elastic recoil, powers the movement. Toads of the genus Bufo possess an elastic recoil system of mouth opening that powers inertial tongue projection, and toads show low temperature dependence for the average velocity (Q₁₀ of 1.04), maximum velocity (Q₁₀ of 1.10), and maximum acceleration (Q₁₀ of 1.16) of ballistic mouth opening. Ranid frogs are known to use inertial elongation for tongue projection to capture prey, as Bufo does, using an independently evolved mechanism. We analyzed the kinematics and dynamics of feeding in Rana pipiens to test whether an elastic mechanism is operating as in Bufo. Feeding events at 10, 15 and 25°C were imaged at 6000 Hz and excursions, durations, and average velocities of jaw and tongue movements were measured from the image sequences. Ballistic mouth opening had a Q₁₀ value of 1.17 for average velocity, and 1/Q₁₀ value of 1.12 for duration. The gape at the end of ballistic opening showed a Q₁₀ of 0.97. The duration of tongue projection showed an inverse Q₁₀ of 1.11. In contrast, the average velocities of the transport phase of mouth opening, during which the gape widens to accommodate prey, and of mouth closing showed Q₁₀ values of 1.90 and 1.87 respectively, revealing greater thermal dependence as found in Bufo. The temperature independence of the ballistic phases of inertial elongation suggests a elastic mechanism in Rana pipiens similar to that of Bufo. Inertial elongation is hypothesized to have evolved convergently in Rana and Bufo, and our findings suggest convergent evolution of the underlying elastic recoil mechanism as well.