Rapid Gustatory Food Evaluation in Fish

Abstract

Fish have a well-developed sense of taste and can evaluate the palatability of grasped food and reject it if food do not match an expected quality. In the present study the food retention time was measured in Eurasian minnow Phoxinus phoxinus for agar pellets flavoured with amino acids (L-alanine, L-proline, L-phenylalanine; 0.1 M) by analysing video recordings. About 50% of the pellets were rejected within less than 145 ms. The shortest periods for pellet retention were within 42 ms. The mean values vary between 260 and 370 ms for pellets flavoured with amino acids but no significant difference was found between rejection time for pellets with palatable alanine, aversive phenylalanine and ineffective proline. It means that rejection time is not related to the palatability of grasped food item and indicates that there is a short-cut in the neurophysiological pathways that makes the fish reject the grasped food items with minimum delay. The fast rejection helps fish to decrease time for unproductive efforts and increase the possibilities to find valuable food after new search.