Food search behavior in arctic charr,Salvelinus alpinus (L.), induced by food extracts and amino acids.

Food search behavior in Arctic charr (Salvelinus alpinus) to extracts of granulated food was quantified and compared with the response to solutions of amino acid mixtures. The concentration of each of 18 amino acids was analyzed in the food extract and similar pure amino acid solutions were prepared. Earlier published electrophysiological data and the data of concentrations in the test area were used to order the amino acids with respect to their presumed contribution to the stimulatory effect of the food extract. The 18 amino acids were tested collectively (18 aa) or were divided into two groups, one group containing 7 amino acids (7 aa) which was presumed to have a high stimulatory effect and the other group containing the remaining 11 amino acids (11 aa). The solutions of 7, 11, and 18 aa were stimulatory at concentrations between 2 and 5 × 10(-6) M, but no significant responses were observed at 2-5 × 10(-9) M. This can be compared with the food extract which elicited response at all concentrations tested, i.e., the total concentrations of 18 amino acids were 5 × 10(-9), 5 × 10(-8), 5 × 10(-7), and 5 × 10(-6) M. The response to the 18 aa solution was compared with the food extract and was shown to be significantly lower at 5 × 10(-9) M but not at 5 × 10(-6) M. These results show that amino acids induce food search behavior in Arctic charr, but there are other substances which also contribute to the stimulatory effect of the food extract.