Ontogeny of Digestive System of Egyptian Sole (Solea vulgaris): Morphological and Histochemical studies of Larvae and Juvenile Alaa

The aim of the present work is clarifying the ontogeny of the Egyptian Sole digestive system during its larval stage (0DAH, day after hatching) until it become a juvenile (40DAH). The main changes in the morphological digestive tract was detected during its early life at 2DAH (both the mouth and anus are opened). Another day after, the digestive tract of S. vulgaris became longer. After metamorphosis (19-22DAH), the stomach is sac-shaped and limited in its concave side by the liver, occupying the wider part of the cavity. The larvae and juveniles of S. vulgaris have a small stomach, a relatively long intestine. Histochemicaly, a few acidophilic goblet cells appeared scattered between the epithelial cells of the both buccopharynx and esophagus regions. The incipient stomach is distinguished at 3DAH and the mucousa is composed of sulphated mucousubstances. After metamorphosis, an increase in the number of the goblet cells in the esophagus epithelium mucosa is detected. The mucus probably plays an important role in lubrication. Incipient stomach is differentiated into two regions the cardiac and pyloric stomach. The brush border of the intestinal epithelium exhibited acidic mucousubstances activities. Sulphated mucousubstances is mainly localized in the intestinal epithelium. Finally, the digestive system of S. vulgaris is differentiated into 5 portions, buccopharyngeal cavity, and extends through the body as esophagus, cardiac and pyloric stomach and intestine. After 30DAH, the digestive tract shows the same histological organization as in the adult one.