Abstract
This study investigated how visual information about prey location and biomechanical constraints of the feeding apparatus influence the feeding behavior of the tomato frog, Dyscophus guineti. When feeding on prey at small azimuths (less than ± 40°), frogs aimed their heads toward the prey but did not aim their tongues relative to their heads. Frogs projected their tongues rapidly by transferring momentum from the lower jaw to the tongue. Storage and recovery of elastic energy by the mouth opening muscles amplified the velocities of mouth opening and tongue projection. This behavior can only occur when the lower jaw and tongue are aligned (i.e., within the range of motion of the neck). When feeding on prey at large azimuths (greater than ± 40°), frogs aimed both the head and tongue toward the prey and used a muscular hydrostatic mechanism to project the tongue. Hydrostatic elongation allows for frogs to capture prey at greater azimuthal locations. Because the tongue moves independently of the lower jaw, frogs can no longer take advantage of momentum transfer to amplify the speed of tongue projection. To feed on prey at different azimuthal locations, tomato frogs switch between alternative strategies to circumvent these biomechanical constraints.
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Acknowledgments
This research was supported by grants IBN-0215438, IBN-0240349, IOS-0623791, and IIS-0827688 from the National Science Foundation. Helpful comments on earlier versions were provided by Jean Block, Carrie Carreno, Leslie Gilmore, Marci Hollenshead, A. Kristopher Lappin, Stan Lindstedt, Laura Krebs, Maureen Maloney, Erika Nowak, David Pierotti, and Eric Zepnewski. We also thank two anonymous reviewers for their insightful comments on previous versions of this manuscript. The experiments in this study were conducted in accordance with NIH publication No. 85-23, “Principles of laboratory animal care” and with the approval of the Institutional Animal Care and Use Committee at Northern Arizona University.
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Monroy, J.A., Nishikawa, K.C. Prey location, biomechanical constraints, and motor program choice during prey capture in the tomato frog, Dyscophus guineti . J Comp Physiol A 195, 843–852 (2009). https://doi.org/10.1007/s00359-009-0463-2
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DOI: https://doi.org/10.1007/s00359-009-0463-2