Pineal of fish Bagarius bagarius (Hamilton) and structure of photoreceptor cell

Abstract

The pineal organ of fish Bagarius bagarius is situated in the cranium in the undersurface of skin covering pineal foramen and consists of pineal sac, pineal thalamus and pineal stalk. The pineal sac is trilobed rossette like with swollen base and surrounded by connective tissue capsule. The parenchymatous layer of lateral and ventral wall are thick dorsal wall is thin. Villi from latero-ventral wall protrude into the lumen which contains photoreceptor, supporting, astrocyte, ganglion and endothelial cells. The thalamus is swollen base of sac and the stalk is long thread like structure. The photoreceptor cells are elongated cucumber shaped consisting of dumble-shaped inner segment and outer segment. Inner segment has a nucleatd basal lobe with a irrigular wavy indented nuclear membrane, a cytoplasm with rich golgi bodies, globular vesicles, rough walled endoplasmic reticulum, Alfa and Beta granules, less number of oval mitochondria with reticulate cristae and lysosome, synaptic terminals are present at the base which join with processes of Ganglion cells. The non-nucleated apical lobe of inner segment is densely packed with mitochondria and is constricted at the junction of basal lobe forming