Morphological changes in digestive tract of Atlantic sturgeon Acipenser oxyrinchus during organogenesis

The histological development of the digestive tract of Atlantic sturgeon Acipenser oxyrinchus larvae were studied from 6th to 49th day post hatching (dph). The majority of developmental changes in the Atlantic sturgeon larvae took place during the first days after hatching. In Atlantic sturgeon larvae, digestive tract development started from the spiral intestine and proceeded frontward, similarly as in other sturgeons. During the endogenous feeding phase, the wall of the yolk sac differentiated into the stomach (glandular and non-glandular regions) and the anterior and intermediate intestine, while the hind-gut primordium differentiated into the spiral valve and rectum. At on first exogenous feeding (10 dph), the digestive tract consisted of a well developed buccal cavity, oesophagus, glandular and non-glandular stomach, anterior intestine, spiral intestine and anus. The absorptive surface area of the sturgeon intestine increased during development due to the elongation of the intestine and formation of pyloric caeca between 6th -20th dph. At the onset of exogenous feeding, the organization and cytoarchitecture of the digestive system in Atlantic sturgeon larvae was generally similar to those of juveniles and adults.