Seasonal Histological Comparison of Gonad and Gametogenesis in Female Pearl Oyster (Pinctada radiata) of the Persian Gulf

The pearl oyster, “Pinctada radiate”, is a native species of Persian Gulf area, which has always been attractive for its ability of producing pearl. Thus, studying the gonadal maturation of the pearl oyster has been important for nucleus implantation to pearl production. In this study, samples were taken in winter and spring from Lavan and Kish Islands. The classic histological methods were used to describe the morphology of female gonad, and computer-based image analyzer (Image Tools 2) to measure oocytes areas. Results showed that female gonad was paired organ and asymetrical, situated between mantle and digestive gland. The follicles contained oocytes identifiable in previtelogenin, vitelogenin and postvitelogenin stages. In spring samples compared to winter samples, the connective tissue in follicles shrunk and greater part of follicles space was filled with postvitelogenin oocytes. The means of oocytes surface areas for spring and winter samples were 1276/71±228/6 µm2 and 936/86±237/04 µm2 , respectively. In conclusion, based on observation of female gonad from winter to spring, it was determined that upper stage of maturation occurred and results of previous studies which showed female gonad maturation happened from February to April, before summer spawning, were confirmed.