Vertebrate-Type Steroid Profile in Different Tissues of Wild and Endocrinologically Manipulated Female Brood Stocks of Penaeus monodon

The endocrine mechanism regulating reproduction of tiger shrimp, Penaeus monodon, is a field of topical interest, which is to be addressed in detail as control of reproduction in captivity is conditional for domestication. In this study, the titres of estradiol and progesterone in hemolymph, ovary and hepatopancreas during various reproductive phases of females were quantified using ELISA. Circulating concentration of hemolymph estradiol and progesterone in the endocrinologically-induced (eyestalk ablated) females was also quantified. Additionally, the evidence for estradiol and progesterone receptors was provided using immunohistochemistry. Levels of progesterone in hemolymph and ovary were highest in the vitellogenic and ripe phases (P > 0.05). Conversely, in hepatopancreas significantly higher progesterone level was detected at immature phase (184.3 ± 2.3 pg/ml). Estradiol was highest in hemolymph (65.97 ± 0.8 pg/ml) and ovary (58.47 ± 0.7 pg/ml) at the early vitellogenic phase. In hepatopancreas, however, lowest level of estradiol was detected at the early vitellogenic phase (121 ± 0.38 pg/ml). Progesterone and estradiol receptor protein signals were predominantly found in the pre vitellogenic oocytes. These results suggest the possible involvement of vertebrate-type steroid in the reproductive maturation of P. monodon.