Seasonal Changes in Hypothalamo-Hypophysial Complex in relation to reproduction in murrel fish Channa punctatus (Bloch).

Abstract

Seasonal changes in the secretory activities of hypothalamic nuclei, the nucleus preopticus (NPO) and nucleus lateralis tuberis (NLT) and pituitary gonadotropic cells were studies in relation to reproductive cycle of a fresh water murrel fish Channa punctatus. Hypothalamo-neurosecretory complex consisted mainly of NPO, NLT and their axonal tracts. NPO is a paired structure situated on either side of third ventricle anterodorsal to the optic chiasma. NPO consists of dorsal pars magnocellularis (PMC) of larger and ventral pars parvocellularis (PPC) of smaller neurosecretory cells. The NLT is situated at infundibular floor region adjacent to pituitary gland. NLT cells are of two types, the larger NLT-I cells generally, placed on the anterolateral side and the smaller NLT-II cells posteroventral region in the infundibular floor adjacent to the pituitary gland. NPO and NLT cells of hypothalamus and pituitary gonadotropic cells exhibit conspicuous seasonal changes in relation to reproductive cycle. During resting phase these cells remain inactive and show poor concentration of neurosecretory granules and glycoproteinous contents in the pituitary gonadotropic cells. Progressive increased synthesis of granules occur during preparatory phase. During prespawning phase these cells exhibit maximum synthetic activities as they were laden with the neurosecretory / hormonal materials whereas they exhibit degranulation and partial vacuolisation (releasing activities) during spawning phase. These cells sharply release their contents during postspawning phase showing depleted appearance with increased vacuolisation.