Résumé
The effect of different dietary protein and lipid levels in the expression of several digestive genes during the early development of Pseudoplatystoma punctifer, an Amazonian catfish with high aquaculture potential, was evaluated. Larvae were fed Artemia nauplii from 4 to 12 days post fertilization (dpf) and weaned from 13 dpf onto compound diets containing different protein:lipid levels (30:15, 30:10, 45:15 or 45:10). The expression of trypsinogen-try, chymotrypsin-chy, amylaseamy, lipoprotein lipase-lpl, phospholipase-phl and pepsinogen-pep was analyzed at the end of the Artemia (12 dpf) and compound diet (26 dpf) feeding periods in order to better understand the digestive function and nutritional needs of this species. Except for pep expression, that was highest in 45:10 group, no differences were found in the expression of the analyzed digestive genes during the Artemia feeding period (12 dpf). However, digestive genes were differentially modulated by the different compound diets (26 dpf). Tryp, amy, phl and pep expressions were highest in 45:15 group, whereas lpl expression was highest in 45:10 group and lowest in 30:15 and 30:10 groups. Groups 30:15, 30:10 and 40:10 showed similar levels of amy and phl expression. Try expression was lowest in 30:10 group followed by 30:15 and 45:10 groups, whereas the lowest pep expression was observed in 30:15 and 30:10 groups followed by 45:10 group. No significant differences were found in chy expression among the four dietary treatments. Try and lpl expressions increased during development in all groups with the exception of groups 30:10 and 30:15, respectively. Phl expression increased during development in 45:15 and 45:10 groups while it remained stable in the others. Chy expression decreased during development in 45:10 group and amy expression increased during development in 45:15 group whereas their expression remained invariable in the rest of the groups. Pep expression increased during development in all dietary groups. In conclusion, the dietary protein and lipid content and their ratios modulated the digestive function in P. punctier early juveniles. Thus, the better growth and survival and the lower incidence of cannibalism observed in 45:15 group might be explained by the better digestive performance showed by these individuals.