Graduation Year

2012

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Biology (Integrative Biology)

Major Professor

Stephen M. Deban

Keywords

Anurans, Ectotherms, Elastic mechanism, Feeding, Inertial elongation, Q10

Abstract

Ectotherms such as frogs must either function within environments with temperatures amenable to their physiological needs, or find means to reduce the impact of temperature on their activities. Recent studies on reptile and amphibian feeding have shown convergent use of elastic recoil to drive feeding movements, thereby decoupling temperature's effects on muscle from movement and allowing the animals to feed over broader temperature ranges. Rana pipiens specimens (n=5) were exposed to three ambient temperatures (10°, 15°, and 25° C) at which feeding behavior was imaged at 6000 Hz. The image sequences yielded detailed kinematic and dynamic information for jaw, tongue, and body movements, including velocity, acceleration, power, duration, and excursion. Previously published studies have examined feeding in ranid frogs; however, those studies employed slower frame rates that did not permit analysis of instantaneous accelerations and velocities, and depressor and jaw-tongue complex mass specific power outputs in Rana feeding have not yet been established. Specimens were dissected for morphological measurement and calculation of mass-specific dynamics relative to the m. depressor mandibulae and the center of mass of the jaw-tongue complex. Previous studies on tongue projection in Bufo terrestris have shown that the rapid jaw depression that inertially elongates the tongue relies on elasticity in the depressor muscles. Further, because this movement is elastically driven, it is less sensitive to temperature than a completely muscle-driven movement would be. Because Rana also feeds through inertial elongation of the tongue (as does Bufo, in which the mechanism is convergent), I hypothesized that Rana would demonstrate thermal insensitivity in its feeding kinematics and dynamics in a pattern similar to that documented in Bufo. Experimental results indicated that portions of the feeding cycle related to the initial, ballistic phase were at least moderately thermally insensitive. At all temperatures studied, Rana reached approximately half of the depressor mass-specific power of Bufo, demonstrating that Bufo's depressor mass-specific power output is not the minimum value necessary for inertial elongation. I further hypothesize that thermal independence and power output in excess of that achievable by muscle alone during the initial, ballistic mouth opening phase of feeding suggests the involvement of an elastic mechanism convergent with that of Bufo terrestris.

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