Experimental and seasonal changes in the pituitary of the Teleost Heteropneustes fossilis (Bloch).

The pituitary of Heteropneustes fossilis is composed of a glandular adenohypophysis and a neurohypophysis (NH). The adenohypophysis is divided into three regions namely: rostral and proximal pars distalis (RPD and PPD) and pars intermedia (PI) consisting of seven different cell types. The RPD is made up of two cell types, the erythrosinophilic acidophils which form the major component of this region and H. Pb positive cells which border the NH. The latter exhibited hypertrophy during spawning and in radiothyroidectomised fishes. The erythrosinophils and H. Pb positive cells can be compared to the lactotrophs and corticotrophs described in the literature. The PPD is composed of three cell types: thyrotrophs, gonadotrophs and acidophils. The gonadotrophs and thyrotrophs readily take up the PAS, aldehyde fuchsin and anilin blue. The gnadotrophs show a marked numerical increase and hypertrophy in the breeding season, whereas they are small and comparatively few in nonbreeding season. In radiothyroidectomised fish the thyrotrophs show hypertrophy and degranulation and tendency to migrate into all the component parts, reaching upto the stalk region. In the control only few cells compared to thyrotrophs are seen in the NH and PI. The PI consists of H. Pb and PAS positive cells. They may be involved in the secretion of melanocyte stimulating hormone (MSH) and osmoregulation as suggested in the literature.