Effect of exogenous estrogen on the ovarian development and gene expression in the female swimming crab Portunus trituberculatus (Miers, 1876) (Decapoda: Brachyura: Portunidae)

Ovarian development in crustaceans is known to be controlled by neuropeptides and steroid hormones. We evaluated the effects of an exogenous steroid hormone, 17 beta-estradiol (E-2), on survival rate, ovarian development, and expression levels of genes functionally involved with ovarian development in female Portimus trituberculatus (Miers, 1876). The in vivo injections of E 2 dramatically enhanced E-2 levels in the hemolymph and promoted ovarian development in female crabs. The highest gonadosomatic index (GSI) was found in E-2 injections of 1 mu g g(-1) body weight (P< 0.05). No significant differences were found on the survival and hepatosomatic index (HSI) among all treatments. The quantitative real-time PCR (qRT-PCR) data indicated that the transcripts of vitellogenin (Vg) gene were enhanced by E-2 injection in both ovary and hepatopancreas, whereas there were no significant differences on the expressions of estrogen-related receptor (ERR), retinoid X receptor (RXR), and ecdysone receptor (EcR) in ovary, as well as ERR and RXR in hepatopancreas of female crabs (P> 0.05). E-2 significandy induced the gene expression levels of EcR-mRNA and RXR-mRNA in the cerebral ganglion (P > 0.05), but suppressed ERR-mRNA expression in the same organ (P > 0.05). E-2 clearly promoted the levels of ERR-mRNA and RXR-mRNA in the eyestalk of females for all E, injection treatments. The significantly higher expression levels of EcR-mRNA and RXR mRNA were also found in the mandibular organ of females after E-2 injection in some treatments (P > 0.05). These results suggest that E, injection might indirectly stimulate the ovarian development and vitellogenesis in female P.trituberculatus by mediating the secretion of hormones and gene expression in the endocrine organs (e.g., eyestalk and mandibular organ).