Immunorecognition and distribution of progestin receptor in the swimming crab Portunus trituberculatus during ovarian development

Progesterone is one of very important sex steroid hormones,which plays an important role during the ovarian development of crustaceans.In vertebrate,progesterone regulates the reproduction generally via progestin receptor(PR).Previous studies have shown PR is present in the ovary,hepatopancreas and nervous tissues for some crustacean species.The swimming crab,Portunus trituberculatus,is a commercially important fisheries resource and mariculture species in East Asian countries.The better understanding of reproductive mechanism would potentially benefit artificial propagation as well as fisheries management of P.trituberculatus.The present study was conducted to immunorecognize and immunolocalize PR in the ovary,hepatopancreas,mandibular organ,Y-organ,optic ganglia and thoracic ganglion mass of female P.trituberculatus via Western-blotting and immunohistochemistry.Then,the change and distribution of PR was also investigated in these tissues during the ovarian development of female P.trituberculatus.The results showed that PR with an apparent molecular weight of 100 ku was identified in the optic ganglia of female P.trituberculatus.By means of immunohistochemistry,PR was detected in the ovary,hepatopancreas,mandibular organ,optic ganglia and thoracic ganglion mass.During the ovarian development of female P.trituberculatus,the follicule cells were stained with strongly positive PR at each ovarian stage.As for the germinal cells,the strongly positive PR only exsited in the cytoplasm from the early ovary developmental stages,including stagesⅠ,Ⅱ and Ⅲ,while the strongly positive PR was stained in the nucleus of germinal cells during the stage Ⅲ to stage Ⅴ.For the female hepatopancreas,PR was mainly localized in the cytoplasm and nucleus of the fibrillar cell at all ovarian developmental stages,and PR was also present in the nucleus of stage Ⅲ resorptive cell.On the contrary,no positive PR-like substance was found in the other types of hepatopancreas cells,such as blister-like cell and embryonic cell during the ovarian development of female P.trituberculatus.As for the endocrine organ,PR was only localized in the cellular cytoplasm of the stage Ⅳ mandibular organ while positive PR-like substance was not found in the gland cell of Y-organ.Moreover,PR-like substance was also detected in the nervous tissues of female P.trituberculatus.As for the optic ganglia,PR was mainly localized in nerve cells from stage Ⅲ to stage Ⅴ.In addition,PR was also localized in the thoracic ganglion mass.Nerve cell and nerve medulla were stained positively with PR-anti-body from the ovarian stage Ⅰ to stage Ⅴ.In conclusion,these results suggest that progesterone not only can regulate the vitellogenesis and ovarian development directly via interacting with PR in ovary and hepatopancreas,but also may indirectly modulate ovarian development through the synthesis and secretion of other endocrine hormones.