Ultrastructural study of the pituicytes in the pituitary gland of the teleost Diplodus sargus

An electron microscopic study was performed on the pituitary gland of the Mediterranean teleost fish Diplodus sargus to analyse the morphological characteristics of the pituicytes. In this class of vertebrates, the pituicytes have, like other astroglial cells, a trophic and support function, but they may also play an active role in the release of neurohormones. Most of the pituicytes were of the Dark type. Their shape appeared irregular with long, thin processes protruding from the cellular body. The pituicytes protruded from the neurohypophysis as far as the adenohypophysis. Their cellular bodies were mainly located in the posterior neurohypophysis. In the adenohypophysis, pituicytic processes were intermingled with cells of the pars intermedia and pars distalis, though being more numerous in the former. These processes sometimes surrounded the whole adenohypophyseal cell. This provides further evidence for the possible role of the pituicytes in controlling the release of the pituitary hormones given that, in teleost fishes, there is no distinct portal system or true median eminence.