Comparative histophysiology of pancreas in Cirrhinus mrigala (Hamilton, 1822), Oreochromis niloticus (Linnaeus, 1758) and Wallago attu (Bloch & Schneider, 1801)

Abstract

The disposition, cellular organisation and biochemical nature of the exocrine pancreas were studied in three species of fishes viz., the mrigal, Cirrhinus mrigala, the Nile tilapia, Oreochromis niloticus and the wallago, Wallago attu using histological and histochemical techniques. Histological analysis demonstrated that the pancreatic tissues were dispersed within the hepatic parenchyma as a hepatopancreas in C. mrigala and O. nilotica. The structural analysis also showed that in C. mrigala, pancreatic tissues were also diffused within the spleen and in the adipose tissues among the intestinal coils. However, in W. attu, the discrete pancreatic tissue formed distinct acini interspersed with clear islet of Langerhans. In all the three species, the exocrine acinar cells were pyramidal, triangular or rhomboid in shape containing basal nucleus and apical densely packed zymogen granules. Histochemical study revealed that the zymogen granules of exocrine acinar cells of all the three species exhibit different intensities of tryptophan content, which is the precursor of various pancreatic enzymes. This is probably due to the variation in feeding habits of the species concerned.