AMINO-ACID PROFILES AND AMINO-ACID UTILIZATION IN LARVAL AFRICAN CATFISH (CLARIAS-GARIEPINUS) - EFFECTS OF ONTOGENY AND TEMPERATURE

The present study investigated the qualitative amino acid (AA) require ments of larval African catfish Clarias gariepinus. Yolk-sac larval AA profiles were measured at different temperatures and also in animals reared at 28 degrees C fed Artemia nauplii or an experimental dry diet . The AA profile of C. gariepinus larvae changed during ontogeny, espe cially before the start of exogenous feeding. The AA profiles of the f ood items (yolk, Artemia and the dry diet) differed considerably from that of the larvae. No selective absorption of yolk AA was detected. H igher temperatures led to increased absorption and depletion rates of AA, and also to a higher retention efficiency of yolk nutrients. Howev er, changes in temperature did not induce preferential absorption or d epletion of individual AA, and caused only small variations in the AA profile. Depletion rates of individual AAs varied, possibly due to dif ferences between larval and yolk AA profiles, and also to changes in t he larval AA profile during ontogeny. There was little regulation of c atabolism of individual AA in yolk-sac and starved larvae, and no spar ing of essential AA.