Ontogeny of the digestive tract of Centropomus parallelus larvae.

Development of the digestive tract and accessory glands of larvae of the fat snook Centropomus parallelus was examined under light microscopy, from hatching to 60 day post-hatching (dph). At hatching, the digestive tract is straight and composed by a cubic cell layer. The exogenous feeding starts at 3 dph, concomitantly with the mouth opening and subdivision of the rudimentary stomach and esophagus. At 4 dph, the intestine has three sectins, and vacuoles are observed in the posterior section, indicating the beginning of protein digestion and absorption. The pharyngeal teeth appear at 9 dph, and goblet cells appear at 13 dph in the esophagus. Gastric glands appear at 30 dph, marking the beginning of weaning. The disappearance of supranuclear vacuoles in the posterior intestine occurs at 35 dph, suggesting efficiency of extracellular digestion. This study shows that C. parallelus larvae is able to start weaning 15 days earlier than reported in earlier studies, increasing the success of larviculture.