Histological structures of Nile Tilapia Oreochromis niloticus Linn. Ovary

Abstract

Basic Histology of female reproductive organ of Nile tilapia Oreochromis niloticus Linn. was studied. Sampling was initiated at the age of 4 months until the age of 8 months. The data on relative ovary weight showed that the GSI of O. niloticus increased in the initial phase and then became stable at the later period. Ovaries were processed by standard histological technique. Histological characteristics of ovarian tissues and oocyte stages were studied by light microscopy. It revealed different histological structure of each oocyte developmental stage: Chromatin nucleolar stage; Perinucleolar stage; Cortical alveoli formation stage; Vitellogenic (yolk) stage; Ripe (mature) stage. Ovarian interstitial tissues were found to consist of interstitial cells, adipose cells, yolk granules and blood capillaries. Oogonial cyst was noted in ovarian tissues of the fish at the age of 5 months. Postovulatory structure, corpora lutea was also observed in the ovary at the age above 6 months. Intraoocytic and extraoocytic deposition of yolk granules and yolk materials was always seen at the age above 6 months. The ovary of the fish that reached the age of 5 months contained all oocytes of different stages.