Histomorphological investigation of Liza aurata (Risso, 1810) (Mugilidae) ovary in the late oogenesis in the Caspian Sea

In the present study, various developmental stages of Liza aurata oocyte, especially IV and V stages have been described. On the basis of histological investigations, oocyte development in L. aurata comprises immature (I), the early maturing (II), the late maturing (III), mature (IV), ripe (V), and spent (VI) stages. In the stages I and II, nucleus occupied large volume of oocyte. Vacuolization and vitellogenesis appearance started at stage III. Vitellogenesis increased by further growth of oocyte at stage IV and also vacuolization occurred. Zona radiata and follicular cells were more conspicuous at this stage. In the late stage IV, number of vacuoles decreased due to fusing of small vacuoles and nucleoli located on different places of nucleus at this stage. At stage V, oocyte normally possessed one or two oil droplets; nucleus disappeared after migration to animal pole. Recently spawned oocytes were fluid, lemon in color and 779.2km in diameter. The maximum gonadosomatic index (GSI) value was found at stage V.