MORPHO-HISTOCHEMISTRY OF THE DISTAL INTESTINES ANDRECTUM OF AFRICAN CATFISH (CLARIAS GARIEPINUS)

The morphology of the farmed African catfish distal intestines andrectum was investigated. The samples were dissected out and the tissue sliceswere passed through graded ethanol, cleared in xylene, embedded in paraffinwax, sectioned and stained for light microscopy. Grossly, the intestine wassubdivided into proximal, middle, distal and rectal regions based on palpablethickness and diameter of the regions. No intestino-rectal valve was observed;hence the rectum was not well defined. The histology revealed the presence oftunica mucosa of simple columnar cells, lamina propria of collagen fibres andmuscularis mucosae of smooth muscle fibres; submucosa of loose connectivetissues and blood vessels; tunica muscularis of smooth muscles in an innercircular and outer longitudinal arrangement; and a serosa in all regions except therectum and anus that presented tunica adventitia. The mucosal folds were fingerliketo orange leaf shaped ingrowths into the lumen on a transverse section. Theydecreased in complexity and height but increased in width towards the rectum.The lining epithelium of the intestinal tract was comprised of the absorptivesimple columnar cells containing goblet cells and intraepithelial lymphocytes.Some rectal simple columnar epithelium contained supranuclear vacuoles whileothers contained non-vacuolated cytoplasm. The goblet cells contained neutraland acid mucins, and increased in number progressively towards the rectum. Theanal tunica muscularis contained mostly skeletal muscles.