SEASONAL CHANGES IN THE PITUITARY GLAND OFA CERTAIN TELEOST FISH IN CORRELATION WITH ITS REPRODUCTIVE CYCLE

Abstract

The present study deals with morphological and histological variations of the pituitary gland of Liza carinata, from the Suez Bay of the Red Sea, in correlation with its reproductive cycle. The study of the reproductive biology revealed that the spawning season of L. carinata extends from late September to late December. The oogenesis of L. carinata is divided into seven stages, namely: the oogonia, the chromatin nucleolar, the early peri-nucleolar, the late peri-nucleolar, the vacuolated, the early yolk globular and the late yolk globular stages. In addition, the spermatogenesis is divided into six stages, namely: the spermatogonia A and B, primary and secondary spermatocytes, spermatids and spermatozoa. The pituitary gland of L. carinata is differentiated into two main divisions, the adenohypophysis and neurohypophysis. The adenohypophysis is further divided into three glandular regions, namely: pro-, meso- and meta-adenohypophysis. The pro-adenohypophysis occupied by acidophils (A1), while the meso-adenohypophysis occupied by both acidophils (A2) and the basophils (B1) and (B2). The meta-adenohypophysis contains the amphiphils (Ml); in addition, the neurohypophysis is formed of a compact mass of nervous tissue. The cells of pituitary gland show no significant seasonal variations all the year round. However, the basophils (B1) seem to be the only gonadotrophs show pronounced seasonal variations.