Induction of vitellogenesis and reproductive maturation in tiger shrimp, Penaeus monodon by 17β-estradiol and 17α-hydroxyprogesterone: in vivo and in vitro studies

Ovarian explants of Penaeus monodon taken from different developmental stages (immature (transparent), immature (yellow), and vitellogenic (green)) were incubated for 24h in medium 199 supplemented with either E-2 or 17-OHP. Exogenous E-2 stimulate Vg mRNA synthesis in the immature (yellow) ovary only, while 17-OHP stimulates mRNA synthesis only in vitellogenic ovary. However, in vitro treatment with both hormones resulted in significant increase in oocytes diameter at higher doses. In vivo assays were carried out by administrating these hormones alone or along with eyestalk ablation at a dose of 9x10(-5)M per individual. After 7days, significantly higher gonadosomatic index resulted in E-2 and 17-OHP treatment along with eyestalk ablation. Further, Vg mRNA transcript level was significantly higher in the group received both 17-OHP and eyestalk ablation. Progesterone and estradiol receptors were characterized using western blotting. Discrete immunoreactive bands of estrogen Receptor (ER) (similar to 78kDa) and progesterone Receptor (PR) (similar to 70kDa) were detected in the ovary of wild brood stock. These findings suggest a reproductive role for these steroidal hormones, which could possibly be used in the induction of maturation and spawning in captive female penaeids.