Hypothalamo-neurosecretory system of the marine teleost, Sphyraena obtusata Cuvier

Abstract

Hypothalamus of Sphyraena obtusata (Family : Sphyraenidae) comprises nucleus preopticus (NPO), nucleus lateralis tuberis (NLT) and their axonal tracts. NPO is a paired structure situated on either side of the third ventricle anterodorsal to the optic chiasma. It is a highly vascularised structure and look inverted L-shape in sagittal section. NPO is divisible into a dorsal pars magnocellularis (PMC) consisting of large neurosecretory cells and pars parvocellularis (PPC) formed of smaller neurons. NLT cells are distributed uniformly in the infundibular floor adjacent to the pituitary stalk. Neurons of PMC and PPC contribute beaded axons to form neurohypophysial tract. Neurosecretory colloid - like material of varying sizes are encountered in NPO. Herring bodies are seen in the anterior as well as posterior neurohypophysis.