Meeting Abstract

63.4  Thursday, Jan. 6  To eat or not to eat: mechanisms of chemical deterrence in food rejection in the blue crab, Callinectes sapidus AGGIO, J.F.*; DERBY, C.D.; Georgia State University jaggio@gsu.edu

Feeding behavior in the blue crab Callinectes sapidus involves finding food, handling it with pereiopods and mouthparts, biting, and swallowing small pieces. The decision to eat depends on the presence of appetitive and deterrent chemicals in the food. When the food is laced with chemical deterrents (e.g., the ink from the mollusk Aplysia californica), one of the most obvious behavioral responses is a marked increase in the handling time, which may be followed by outright rejection of the food. As a first step toward understanding the mechanism of deterrence, we investigated the localization and specificity of the chemoreceptors responsible for rejection using behavioral and electrophysiological techniques. Behavioral observations and ablation studies revealed that the deterrent receptors are not located in the antennules, pereiopods, or maxillipeds. This is further supported by electrophysiological evidence showing that a fraction of Aplysia ink containing aplysioviolin and phycoerythrobilin, which are feeding deterrents, is not a good stimulus for maxilliped chemoreceptors. Two lines of evidence lead us to conclude that the chemoreceptors responsible for rejection are located inside the crabs’ digestive tract. First, a piece of shrimp introduced inside a restrained crab’s mouth will be consumed unless it is laced with a deterrent, in which case it is rejected through oesophageal dilation (i.e., opening the oesophagus and retracting the labrum into the cavity formed). Second, a feeding deterrent applied by itself to the mouth evokes oesophageal dilation. We conclude that deterrence is mediated by receptors located in the oesophagus and are currently attempting to characterize them electrophysiologically. Funded by NSF IOS-1036742 and IOS-0614685.