DISTRIBUTIONAL PATTERN OF DIFFERENT CELL TYPES WITH SPECIAL EMPHASIS ON SEASONAL CHANGES OF GONADOTROPHS IN THE HYPOPHYSIS OF INDIAN RIVER SHAD Gudusia chapra (HAMILTON, 1822) IN RELATION TO OVARIAN MATURITY

Reproduction is a natural phenomenon and it performs under the influence of various external factors which mediate their effect through the hypothalamo-hypophyseal-gonadal subsystem operating as an organic axis bridging the ecological influences and gonadal maturation. Information is collected through the hypothalamus and is passed on to the hypophysis. Hypothalamus releases GnRH which exerts its effect on hypophysis/pituitary to release gonadotrophin hormone from gonadotrophs of Pituitary. Gonadotrophic hormone helps in gonadal maturation and sex steroid production which plays a very important role in oogenesis, final maturation of oocytes. The Pituitary gland of G. chapra is cranio-leptobasic type. It is generally composed of neurohypophysis and adenohypophysis. The adenohypophysis is divided of three parts viz., rostral pars distalis (RPD), middle proximal pars distalis (PPD) and massive pars intermedia (PI). The major part of the RPD occupied by the acidophilic prolactin cells (PRL) stained with acid fuchsin. Fewer adrenocorticotropic cells (ACTH) were scattered among prolactin cells. The basophilic gonadotrophs (GTH) and thyrotrophs (TSH) reacted positively to aniline blue and periodic acid Schiff’s (PAS) were distributed in the anterior and middle part of PPD. The somatotrophs (STH) were the only acidophils that identified. Melanocyte stimulating hormone (MSH) stained with aniline blue and melanocyte concentrating hormone (MCH) stained with acid fuchsin were identified in PI. During growth and maturation phase both GTH and TSH cells were distinguished by intense staining and dense homogenous granules with maximum cellular diameter. During post-spawning phase both cells showed low staining intensity. The seasonal changes in the ovary of G. chapra have been described on the basis of variation in GSI value and frequency percentage of the different female germ cells. The gradual change in the ovarian cycle has been correlated with changes of GTH and TSH cells in pituitary of Gudusia chapra.