Abstract
The ontogeny of the digestive capacities in fish is species-specific and its knowledge is essential for understanding the nutritional requirements of fish larvae. While the Amazon basin contains the world's highest fish biodiversity, the molecular basis of the early digestive physiology has not yet been reported in any Amazonian fish species. In order to increase basic knowledge on the molecular ontogeny of the digestive system of a commercially important Amazonian fish species, six digestive enzyme genes (?-amylase, phospholipase A2, lipoprotein lipase, trypsin, chymotrypsin, and pepsin) were isolated and identified, and their expression analyzed from 3 to 24 days post fertilization (dpf) in Pseudoplatystoma punctifer, a catfish species with high potential for aquaculture diversification. The present results, together with those previously obtained on the development of the digestive enzyme activity, showed that gene expression and enzymatic activities are synchronized and that the enzymatic machinery of P. punctifer was completely prepared for the onset of exogenous feeding (4 dpf, 6 mm total length, TL) and had reached its maturity between 10 and 13 dpf (11-14 mm TL). This indicated that the transition from the larval to the juvenile mode of digestion had been completed and they were suitable for weaning under culture conditions. Furthermore, the gene expression analyses suggest that this species displays an omnivorous behavior with a preference towards carnivory during early development. The present study provides the first comprehensive ontogenetic analysis of the digestive function from a molecular point of view of a species of the genus Pseudoplatystoma, and contributes to the development of feeding strategies in the context of South American aquaculture diversification.