Response changes with growth in the gustatory receptors of young yellowtails (Seriola quinqueradiata)

Laboratory-hatched juvenile yellowtails (mean fork length, 9.3 cm) were rea red for 2 months in two groups on different kinds of food, mysid and squid in one group and fish in the other, and the gustatory neural responses to s even chemicals (adenosine-5'-monophosphate, alanine, arginine, betaine, pro line, tryptophan, and valine) were recorded in fish before and after the 2- month rearing period. Large variances in the responses to some chemicals we re noticed in the juveniles before the rearing experiment. Mann-Whitney U-t ests on the neural responses indicated significant changes in the magnitude of the responses to valine and some other chemicals relative to that for p roline or tryptophan between the pre- and the two post-rearing groups. No s ignificant differences in the response magnitude for the seven chemicals we re observed for the two post-rearing groups suggesting that the response ch anges during: the 2-month rearing might have been intrinsic and not due to specific food items in the diet. The dose-response relationship for some ch emicals was also examined in the juveniles before and after the 2-month rea ring. A slight lowering of threshold was noticed for alanine and valine aft er the rearing. Data on the responses of wild yellowtails were in support o f the changing responsiveness of gustatory receptors during development of juvenile yellowtails.