Size-related performance variation in the wood frog (Rana sylvatica) tadpole tactile-stimulated startle response

Abstract

I described the initial response of the Rana sylvatica LeConte, 1825 tadpole to predator contact, that is, the tactile-stimulated startle response (TSR). Because tadpole survival from predation increases with tadpole size and with exposure to chemical predator cues during development, I anticipated that TSR performance would vary accordingly among tadpoles. Startle responses were stimulated in a laboratory setting and filmed using high-speed video. This method allowed analysis of performance at fine spatial and temporal scales. Maximum acceleration performance increased with tadpole length, as did cumulative distance covered after the first 0.016 s of the response. In contrast, the cumulative distance covered during the initial instants of the response did not depend on tadpole size. Exposure to a predator cue (odor of the dragonfly naiad Anax junius (Drury, 1773)) during development had no effect on tadpole morphology. Predator-cue exposure negatively affected cumulative distance traveled after the first 0.072 s of the startle response. I concluded that size-dependent variation in performance of the TSR may partially explain differential survival of tadpoles, but there was no evidence that exposure to this predator cue increased TSR performance.

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

“…However, in many cases, the orientation at the end of stage II was different from the original. In a previous study encompassing a broader size range of wood frog tadpoles, I showed a similar pattern: the average rotation of wood frog head/body during stage I was 1301 and, during stage II, rotation averaged 1131, almost reversing stage I rotation (Eidietis, 2005). The median head/body orientation at the end of stage II was very close to the original orientation (Fig.…”

“…As noted above, researchers report that the first two stages of the tadpole TSR include short, time-dependent peaks in linear acceleration of the head/body (Hoff, '88;Wilson and Franklin, '99, 2000;Eidietis, 2005). Similar time dependence of rotational acceleration has not yet been described.…”

“…Similar time dependence of rotational acceleration has not yet been described. However, given the changes in rotational direction of the head/body during stages I and II of the TSR (Van Buskirk and McCollum, 2000;Eidietis, 2005), peaks in rotational acceleration are likely. Resistance to linear acceleration of the head/body R a…”

Trade-offs between size and energy reserves reflect alternative strategies for optimizing larval survival potential in rockfish

“…Taken together, their positive association with body size across species suggests that larger larvae will have substantially greater success in avoiding predation and are likely to do much better than smaller larvae under conditions of high predator density. Increasing escape capabilities with increasing body size have been commonly observed for larval fishes and amphibians (Batty et al 1993, Williams et al 1996, Fuiman et al 1999, Wesp & Gibb 2003, Eidietis 2005. We did not observe a correlation between larval size and startle performance within species, but this was likely due to the relatively narrow size range within individual species (CV ranged from 2.9 to 3.3% within a species, but was 6.0% for the means of each of the 5 species).…”

Chronic exposure to fluoxetine (Prozac) causes developmental delays in Rana pipiens larvae

“…This size-specific predation is observed in part because faster-growing tadpoles quickly become too large for the gape size of certain predators [25,31]. Moreover, weight is generally correlated with swimming speed [32,33], so, although no differences in swimming speed among treatments were found in this study because we controlled for size, fluoxetine may indirectly impact swimming speed by decreasing larval size. Therefore, exposed tadpoles may be less capable of escaping predation because of decreased swimming speed caused by retarded development.…”