Anatomical , histological and histochemical studies of digestive tract of fish Mastacembelus mastacembelus

Abstract

The present study involves anatomical comparsion, histological and histochemical structures of digestive tract ofMastacembelusmastacembelus (carnivore) at the level of light microscope hematoxylin and eosin , mallory's triple , periodic acid schiff (PAS) , and alician blue stains (PH1and PH2) were use . The anatomical Results revealed cylindrical muscular tube esophagus connecting pharynx , directly to cardic stomach of M. mastacembelus .The stomach shape is cystoid with cardic, fundic and pyloric portions . Pyloric caeci absent in M. Mstacembelus.intestine is shortest, relative length (RGL) is (0.58) , (S) letter shape and not coiled . Histologically the esophagus of M. Mstacembelus composed of two parts, anterior and posterior parts .The stomach has cardic , fundic and pyloric portions while intestine divided into four parts, proximal , middle, distal and anus .The arrangement and number of strata forming digestive wall from esophagus up to anus is similar in studied fish , involving four basic layers (mucosa , submucosa , mascularis and serosa) . Tunica muscularis along the digestive canal consist of two smooth muscle layers inner (circuler) and outer (longitudinal) expectesophagus which included stratified muscle layers . Many mucosal folds were lining digestive tract. These folds become crowded, very long and branched along all intestinal divisions and then become very short in anus . Tunica mucosa consist of simple columnar epithelium lining G.I from esophagus to anus . Goblet cells present among esophageal, intestinal and anal mucosal epithelium . They are numerous along esophagus and posterior intestine . Lamina propria directly under mucosal epithelium consists of thick layer of Connective tissue present in anterior esophagus, stomach and intestine . Lamina propria contain great amount of gastric glands consist of oval or spherical secretory unit lined by one type of pyramedial cell. Posterior stomach mucosal surface contains great amount of gastric pit. muscularis mucosa absent in M. mastacembelus. Tunica submucosa along digestive canal of studied fish consist of thin areolar connective tissue and collection of lymphatic cells similar to lymphatic follicle seen in anterior intestine . G.I serosa layer consist of connective tissue covered bymesotheliur. This study showed the presence of different amounts and types of mucous material in different G.I regions . positive tissue reaction with PAS, AB1, AB2 ensure presence of mucous material . Tissue reaction with PAS was very strong in esophagus and intestine while it was strong in stomach while tissue reaction withAB2 was moderate in esophagus, stomach and intestine .