Histological and surface ultrastructural observations on the saccus vasculosus of Eutropiichthys vacha (Hamilton)

Abstract

The histological architecture and ultrastructural characteristics of saccus vasculosus in Eutropiichthys vacha (Hamilton) were investigated by employing light and scanning electron (SEM) microscope. The saccus vasculosus is small, oval shaped structure, situated on the ventral side of the diencephalon behind the pituitary. This circumventricular organ contained a typical large central lumen lined by characteristic coronet cells and supporting cells. The coronet cells possessed basally placed nuclei and intense apical secretion. The supporting cells were few in number and placed in between coronet cells. Under SEM observations the coronet cells were variable in shape and apical parts were provided with different shapes of globular protrusions. The supporting cells were fusiform in structure and arranged in between coronet cells. The coronet cells were attached with dense blood vessels. The intense reaction of silver stain was marked in the terminal end of coronet cells and nevers were attached with blood vessels. Under SEM observations the nerve fibres and blood vessels of different calibers were also found attached with the coronet cells. Various cells linining the epithelium of saccus vasculosus and their physiological activities in E. vacha have been discussed.