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IS POST-FEEDING THERMOTAXIS ADVANTAGEOUS IN ELASMOBRANCHS?
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IS POST-FEEDING THERMOTAXIS ADVANTAGEOUS IN ELASMOBRANCHS?

Valentina Di Santo
University of West Florida
Master of Science (MS), University of West Florida
2009

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Abstract

Thermotaxis has been suggested as a means for elasmobranch fishes to improve the efficiency of metabolic processes such as digestion. For shuttling to be effective, temperature mediated movements must affect absorption and evacuation rates differently a result that, to date, has never been empirically demonstrated. In this study, the post-feeding thermotaxis hypothesis was tested in the laboratory using two elasmobranch species, the Atlantic stingray, Dasyatis sabina (Lesueur), which inhabits thermally variable environments, and the whitespotted bamboo shark, Chiloscyllium plagiosum (Anonymous [Bennett]), a stenothermic fish living on Indo-Pacific reefs. Experiments at temperatures similar to those experienced in nature reveled that temperature change had no significant effect on bamboo shark absorption (p = 0.372) or evacuation rates (p=0.245), suggesting that stenothermic sharks may lack the ability to exploit temperature differences as a means to improve digestion efficiency. On the other hand, Atlantic stingrays showed significantly lower evacuation (p < 0.001) and absorption (p < 0.001) rates at lower temperatures. The relative decrease was greatest for evacuation (Q10=3.08) than absorption (Q10=2.20), resulting in a significant increase in total absorption (p<0.001). Thus, Atlantic stingray may benefit from using shuttling behavior to exploit thermal variability in their environment thereby maximizing energetic uptake.
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