Behavioural responses of glass eels of Anguilla anguilla to non-protein amino acids

Glass eels reacted chemotactically towards five non-protein constitutional amino acids, D-glutamine, D-asparagine, D-glutamic acid, D-alanine and beta -alanine, disserved in fresh water or salt water, with behavioural threshol ds ranging from 10(-9) M for the most effective (D- and beta-alanine) to 10 (-7) M for the other three. With the exception of D-asparagine in fresh wat er and D-alanine at concentrations greater than or equal to 10(-7) M, these amino acids were strong attractants. The results are compared with previou s findings on the respective L-isomers. The non-protein amino acids may inf luence behaviour in the search for food and the recognition of conspecifics . (C) 1998 The Fisheries Society of the British isles.