Histophysiological and surface ultrastructural studies of the saccus vasculosus of Notopterus chitala (Hamilton)

We investigated the cytoarchitecture and surface ultrastructural characteristics of different cells lining the epithelium of the saccus vasculosus of Notopterus chitala (Hamilton, 1822). The saccus vasculosus, the richly vascularized reddish, sac like organ is situated on the ventral aspect of the diencephalon just behind the pituitary gland. Histologically, the saccus vasculosus consisted of several loculi lined with a heterogeneous population of a large number of specialized coronet cells and a smaller number of alternately arranged supporting cells. The loculi were densely surrounded by blood sinusoids. The loculi opened into several collecting channels that united and ultimately drained into the third ventricle of the brain. The coronet cells possessed central or basal nuclei and an apical globular protrusion. Under scanning electron microscopy, the coronet cells were variable in shape with prominent nuclei. The supporting cells were triangular in shape and placed in between the coronet cells. The apical parts of the coronet cells had different shapes of globular protrusions with distinct stalks. Intense silver stain was noted in the terminal end of the coronet cells and nerves were attached with blood vessels. Under scanning electron microscopy observation, nerve fibers of different caliber were attached to the coronet cells and blood vessels. The various cells of the saccus vasculosus in N. chitala were correlated with their functional significance.