Hypothalamo-neurosecretory system of the female sea bass, Lates calcarifer (Bloch), with special reference to gonadal maturation

Abstract

Hypothalamus of Lates calcarifer (Family : Centropomidae) consists mainly of nucleus preopticus (NPO), nucleus lateralis tuberis (NLT) and their axonal tracts. NPO is a paired structure situated on either side of the third ventricle slightly above the optic chiasma. It is a highly vascularised structure and cytoarchitecturally divisible into dorsal pars magnocellularis (PMC) comprising larger neurons and ventral pars parvocellularis (PPC) with smaller neurosecretory cells. In the hypothalamus the NLT cells were found distributed uniformly in the infundibular floor adjacent to the pituitary stalk. Prominent phloxine-positive neurosecretory material (NSM) was encountered in PPC of matured female. Though neurosecretory cells of both NPO and NLT were positive to aldehyde fuchsin (AF), acid and chrome-alum-hematoxylin-phloxine (CAHP), cellular differentiation was more marked in the latter. Both NPO and NLT contributed beaded axons to form the neurohypophysial tract. Herring bodies (HB) of varying sizes were encountered in the anterior neurohypophysis (ANH). Neurosecretory cells of both NPO and NLT exhibited fluctuations in their secretory activity in response to the gonadal maturation.