Chemoattraction and feeding stimulation in crustaceans

Abstract

Crustaceans utilize water-borne‘chemical signals’to identify and orient toward potential prey. These chemical signals are recognized in spite of the chemical complexity of aquatic environments. Because feeds are a significant expense in all aquaculture operations, the need to maximize feeding rates and reduce wasted feed, thereby lowering production costs, is paramount to economic success. Confusion concerning the function and utility of chemoattractants versus feeding stimulants in aquatic feeds necessitates updated terminology. Simply put, detection does not equal attraction. To accurately describe and predict responses to feeding stimuli, it is necessary first to classify all possible stimulus types and then to categorize behavioural responses to each specific stimulus. The proposed hierarchical behavioural model classifies an animal's response to chemical stimuli into five phases: (1) detection; (2) orientation; (3) locomotion or displacement; (4) initiation of feeding; (5) continuation or termination of feeding. The second step in description of the behavioural model is the association of specific behaviours with these five phases of response. Crustaceans exhibit four major categories of chemotactic behaviour: antennule flicking, which appears to be the most sensitive; probing movements made by the pereiopods that precede locomotion; locomotion by the crustacean, indicating true attraction or repulsion; and movements by the mouthparts that indicate generalized feeding stimulation. Finally, feed and environmental quality have direct effects on the effectiveness of feed attractants/stimulants; food detection and feeding stimulation ultimately determine the commercial value of an aquatic feed.