Occurrence of vertebrate steroids, estradiol 17β and progesterone in the reproducing females of the mud crab Scylla serrata

Abstract

In crustaceans, vitellogenesis is known to be controlled by eyestalk neuropeptides, biogenic amines, ecdysteroids and a juvenile hormone-like compound, methyl farnesoate. In recent years, the occurrence of vertebrate steroid hormones, estradiol 17β (E 2) and progesterone (PG) has also been reported in a few decapods, although their precise role in female reproduction is yet to be determined. The levels of E 2 and PG in the ovary, hepatopancreas and the hemolymph of the red mud crab, Scylla serrata were analyzed in different vitellogenic stages in order to establish a correlation between hormone profile and stages of vitellogenesis. It was observed that the levels of both the steroids increased steeply in the tissues at the onset of vitellogenesis (vitellogenic stage I). Maximum levels of estradiol were present in the hepatopancreas whereas the highest concentration of progesterone was seen in the ovary, suggesting dichotomous roles for these hormones in vitellogenesis. Furthermore, levels of these hormones were estimated in different embryonic stages of the eggs of the sand crab Emerita asiatica and mud crab S. serrata. Their levels fluctuated, following a definite pattern in the different stages, suggesting a possible functional role as morphogenetic hormones. This study, in addition, also reports the presence of E 2 and PG on lipovitellin purified from ovary and eggs as well as vitellogenin purified from the hemolymph implicating a role for these lipoproteins as steroid carriers.