MORPHOLOGY OF THE DIGESTIVE TRACT OF THE FARMED NILE TILAPIA FISH Orechromis niloticus (Linnaeus, 1758) FROM EASTERN NIGERIA

Abstract

The digestive tract morphology of the Nile Tilapia (Orechromis niloticus) was investigated to help understand its
digestive biology, provide data for further studies including clinical cases. The lips, tongue, and oesophagus were
lined by stratified squamous epithelium containing, mucous cells and lymphocytes. This protective type epithelial
covering can be associated with the majorly herbivorous feeding habit. The oesophageal stratified squamous
epithelium contained abundant Periodic Acid Schiff (PAS) positive mucous cells. The U-shaped stomach was
bound cranially by oesophageal sphincter and pyloric sphincter caudally. The stomach mucosal simple columnar
epithelial lining contained PAS positive apical mucin. The laminar propris containing gastric glands were only
seen in the cardiac and fundic regions, the pyloric laminar propria contained well developed PAS positive mucous
glands with myoepithlial cells in the enveloping connective tissue. These mucous glands with further staining
showed a predominance of acid mucin. The intestinal mucosa was lined by simple columnar cells containing
abundant PAS positive goblet cells and lymphocytes. The distal intestine contained aggregated lymphoid cells in
localised areas of laminar propria. From this study, the digestive tract of the farmed Nile Tilapia from Eastern
Nigeria has shown morphological features adaptive for its herbivorous feeding habit in a cultured environment.