The tactile-stimulated startle response of tadpoles: acceleration performance and its relationship to the anatomy of wood frog ( Rana sylvatica ), bullfrog ( Rana catesbeiana ), and American toad ( Bufo americanus ) tadpoles

Abstract

I described the tactile-stimulated startle response (TSR) of wood frog ( Rana sylvatica ), bullfrog ( Rana catesbeiana ), and American toad ( Bufo americanus ) tadpoles. One purpose was to rank species in terms of maximum acceleration performance. Also, I tested whether anatomical indicators of performance potential were predictive of realized performance. TSRs were elicited in a laboratory setting, filmed at 250 Hz, and digitally analyzed. TSRs began with two, initial body curls during which tadpoles showed a broad spectrum of movement patterns. TSR performance was quantified by maximum linear acceleration and maximum rotational acceleration of the head/body, both of which tended to occur immediately upon initiation of motion (<0.012 sec into the response). Bullfrog tadpoles had higher maximum acceleration than the other species, but other interspecific differences were not significant. The species' rank order for the anatomical indicator of linear acceleration potential was bullfrog>wood frog>American toad. The species' rank order for the anatomical indicator of rotational acceleration potential was bullfrog>wood frog=American toad. Thus, the anatomical indicators roughly predicted the rank order of interspecific average performance. However, the anatomical indicators did not correlate with individual tadpole performance. Variability in behavioral patterns may obscure the connection between anatomy and performance. This is seen in the current lack of intraspecific correlation between a morphological indicator of acceleration capacity and acceleration performance. J. Exp. Zool. 305A:348–362, 2006 . © 2006 Wiley-Liss, Inc.