Oesophageal chemoreceptors of blue crabs,Callinectes sapidus, sense chemical deterrents and can block ingestion of food

Abstract

SUMMARYDecapod crustaceans such as blue crabs possess a variety of chemoreceptors that control different stages of the feeding process. All these chemoreceptors are putative targets for feeding deterrents that cause animals to avoid or reject otherwise palatable food. As a first step towards characterizing the chemoreceptors that mediate the effect of deterrents, we used a behavioral approach to investigate their precise location. Data presented here demonstrate that chemoreceptors located on the antennules, pereiopods and mouthparts do not mediate the food-rejection effects of a variety of deterrents, both natural and artificial to crabs. Crabs always searched for deterrent-laced food and took it to their oral region. The deterrent effect was manifested as either rejection or extensive manipulation, but in both cases crabs bit the food. The biting behavior is relevant because the introduction of food into the oral cavity ensured that the deterrents gained access to the oesophageal taste receptors, and so we conclude that they are the ones mediating rejection. Additional support comes from the fact that a variety of deterrent compounds evoked oesophageal dilatation, which is mediated by oesophageal receptors and has been linked to food rejection. Further, there is a positive correlation between a compoundʼs ability to elicit rejection and its ability to evoke oesophageal dilatation. The fact that deterrents do not act at a distance is in accordance with the limited solubility of most known feeding deterrents, and likely influences predator-prey interactions and their outcome: prey organisms will be attacked and bitten before deterrents become relevant.

Bitter tastant responses in the amoeba Dictyostelium correlate with rat and human taste assays

“…The ability to recognize and/or respond to bitter tastants is shared amongst phylogenetically diverse groups, including mammals (Stern et al, 2011), amphibians (Go, 2006;Mashiyama et al, 2014), fishes (Ishimaru et al, 2005), cephalopods (Darmaillacq et al, 2004), decapod crustacea (Aggio et al, 2012), insects and nematodes (Hilliard et al, 2004;Gordesky-Gold et al, 2008;Apostolopoulou et al, 2014). However, data presented here suggest a conserved response from the unicellular Dictyostelium to primates; the last common ancestor of Dictyostelium and multicellular animals existed about a billion years ago (van Egmond and Van Haastert, 2010).…”

Ink From Longfin Inshore Squid, Doryteuthis pealeii, as a Chemical and Visual Defense Against Two Predatory Fishes, Summer Flounder, Paralichthys dentatus, and Sea Catfish, Ariopsis felis

“…Ink from another inking mollusc-sea hares (Aplysia spp. )-is also unpalatable and affects predatory sea anemones (Nolen et al, 1995;Kicklighter and Derby, 2006), crustaceans (Kicklighter et al, 2005;Kamio et al, 2010;Derby and Aggio, 2011;Aggio et al, 2012), and fish (Nusnbaum and Derby, 2010a, b;Nusnbaum et al, 2012). Our work here shows that squid ink is unpalatable to sea catfish but not nearly as much as ink from sea hares, with 1% sea hare ink causing all fish to reject shrimp while 10% squid ink caused rejection in only 36% of encounters.…”

“…Previous work on slow-moving inking molluscs-sea hares, Aplysia spp.-revealed a variety of molecules acting as chemical defenses through a variety of mechanisms (Derby, 2007;Derby and Aggio, 2011). One mechanism is the use of deterrent chemicals, either dietderived or synthesized de novo, that are aversive or unpalatable to predators (Aggio and Derby, 2008;Kamio et al, 2010Kamio et al, , 2011Nusnbaum and Derby, 2010a, b;Nusnbaum et al, 2012;Aggio et al, 2012). A second mechanism is phagomimicry, in which predators are distracted by attractive and appetitive compounds in the ink (Kicklighter et al, 2005).…”

The Role of the Gustatory System in the Coordination of Feeding

“…Other aquatic animals also have multiple taste organs. In blue crabs and leeches engaged in feeding, the rejection of aversive tastants is controlled by internal, and not external, taste sensors (Kornreich and Kleinhaus, 1999; Aggio et al, 2012). In lobsters, taste sensors in the legs are required for a food-clasping response (Borroni et al, 1986).…”