Histomorphological Study of the Cerebral Neuroendocrine System of the Water Beetle, Cybister tripunctatus Ol. (Coleoptera:Dytiscidae)

Neurosecretory cells (NSCs) normally occur in the ganglia of the central nervous system preferably located in the brain. They generally resemble monopolar nerve cells but they are characterized by showing cytological evidence of secretion and usually by discharging their products into the hemolymph. Here, an attempt is made to recognize the NSCs located in various regions of tripartite cerebral lobe of a water beetle, Cybister tripunctatus OL.

Three types of neurosecretory cells have been identified in the cerebral lobes of this adult water beetle. According to the morphological features and staining affinities with Ewen's Paraldehyde Fuchsin (PF) and Heidenhain's Azan-Aniline Blue (A AB) they are classified as 'A', 'B' and 'C' type cells. These cells have been found in certain locations of the cerebral complex, namely, median portion of protocerebrum, lateral region of protocerebrum and tritocerebrum. Thus, three endocrinal centres are present in the brain of this adult insect.