CRUSTACEAN CHEMICAL PERCEPTION: TOWARDS A THEORY ON OPTIMAL CHEMORECEPTION

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Abstract
Experiments explored how crustacea respond to odors that could signal energy and nutrient properties of food. While free amino acids are abundant in living prey, they diffuse rapidly from carrion and are assimilated by biodegradatory bacteria concomitant with release of ammonia. The ratio of amino acids to ammonia decrease with increasing carrion age and is proposed to signal the relative nutritional (nitrogen) quality of food. Supporting this hypothesis are data showing six bathypelagic and littoral species probing and searching to amino acids, but not to ammonia. Amino acids caused forward ambulation (searching) in some species while ammonia induced only tail-flipping (fleeing) in others. Interactions between amino acids and ammonia were clearly antagonistic, since mixtures combining these substances suppressed both feeding and fleeing. Additional experiments with the spiny lobster, Panulirus interruptus, demonstrate that excitation by the high energy molecule, ATP > ADP > AMP = adenosine, which is the pathway followed in autolytic degradation of animal flesh. Solutions identical in ATP evoked searching and feeding according to their ranked order of adenylate energy charge. Results indicate that crustacea respond best to odors that may specify food of highest energy and nutrient content, though responses differ between species and probably reflect differences in dietary habits.