Meeting Abstract

98.1  Thursday, Jan. 7  Temperature effects on the motor control of ballistic prey capture in toads DEBAN, SM*; LAPPIN, AK; University of South Florida; California State Polytechnic University, Pomona sdeban@cas.usf.edu

Elastic structures in musculoskeletal systems can enhance mechanical power output and extend the functional range of muscles. We investigated how elastic recoil mechanisms can also extend the thermal breadth over which ballistic movements can be performed in ectotherms by examining kinematics and motor control of ballistic tongue projection in toads. Bufo terrestris were imaged feeding at a range of body temperatures (12-34°C) with simultaneous recording of EMG activity of jaw levator and jaw depressor muscles. Elastically powered movements (rapid mouth opening and tongue projection) were compared to non-elastic, muscle-powered movements (slow mouth opening, mouth closing, and tongue retraction). Temperature had no significant effect on the velocity of elastically powered movements (Q₁₀ values of 1.0-1.2) but lower temperatures significantly reduced the velocity of muscle-powered movements (Q₁₀ values of 1.4-2.8). Nonetheless, temperature significantly affected muscle activity associated with both elastic and non-elastic movements. With increasing temperature EMG burst duration declined while EMG burst intensity increased (Q₁₀ values of 2.9-3.1). Elastically powered movements are thus less thermally dependent than muscle-powered movements, but temperature has similar effects on the motor control of both types of movement. These results accord with a bow-and-arrow model of ballistic movement in which elements with thermally independent elastic properties (e.g., tendons, non-contractile components of muscle) are strained by active muscle contraction in which the rate of tension development is thermally dependent. The thermally independent elastic elements subsequently recoil to power the ballistic movement.