Seasonal Histology and Histochemistry of the Adenohypophysis of Nile Tilapia (Oreochromis niloticus)

Document Type : Original Article

Authors

Department of Cytology and Histology, faculty of Veterinary Medicine Cairo University.

Abstract

In the present research, the histolo- gy and histochemistry of the adenohypophysis of Nile tilapia were done on 96 sexually mature Nile tilapia fish of both sexes collected monthly from the River Nile at Giza over the period from September 2009 to August 2010. The pituitary gland of both sexually mature male and female Nile tilapia was identically similar during the spring, summer and autumn seasons (breeding seasons). The pituitary gland revealed two well distinguished areas, the adenohypophysis and the neurohypophysis. The adenohypophysis showed three histologically dis- tinct regions: rostral pars distalis, proximal pars distalis, and pars intermedia with no clear demarcation between them. The adenohypophysis was differentiated into two main cellular groups; the chromophobes and chromophils. The chromophils were differentiated into seven types of cells arranged in mosaic appearance; the acidophils (lactotrops and somatotrops); the basophiles (corticotrops, thyrotrops and gonadotrops); and the amphiphils (melano- trops and somatolactotrops). In between the adenhypophyseal cells few cavities either empty or partially filled with an amorphous, non-cellular colloid-like material were present. All parts of the adenohypophysis were penetrated by bran- ching strands of neurohypophyseal tissue, which were coarser and extensive in the pars intermedia. During winter (non-breeding season), the adenhypophyseal glandular cells were smaller, less in field oc- cupation and less in the intensity of their staining reactions.

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