Studies on the histomorphology of the caudal neurosecretory system and its neurohaemal organ of a freshwater teleost, Colisa fasciatus (Bloch and Schneider) (Anabantidae, Perciformes).
The caudal neurosecretory system of Colisa fasciatus has been studied light microscopically. It consists of Dahlgren cells present in the spinal-cord corresponding to the last three vertebrae, their processes and a lobate neurohaemal organ (urophysis) situated inside the centrum of the urostyle. Spinal-cord behind the urophysis continues as filum-terminale. Urophysis may be divided into feabily developed central medulla and well developed peripheral cortex. Herring-bodies are present in the medullary part of the urophysis. Dahlgren cells, their axons and Herring bodies show similar tinctorial responses. They are stainable with acid dyes but do not take up Aldehyde fuchsin and Gomori's chromealum hematoxylin. Present histomorphological study revealed that the urophysis and the caudal neurosecretory system of this fish is highly developed. No sex dependent variation have been observed in the histology of the urophysis and Dahlgren cells of adult females and males.