Role of Oxytocin/Vasopressin-Like Peptide and Its Receptor in Vitellogenesis of Mud Crab.

Oxytocin (OT)/vasopressin (VP) signaling system is important to the regulation of metabolism, osmoregulation, social behaviours, learning, and memory, while the regulatory mechanism on ovarian development is still unclear in invertebrates. In this study, Sp ot/vp-like and its receptor ( Sp ot/vpr-like) were identified in the mud crab Scylla paramamosain. Sp ot/vp-like transcripts were mainly expressed in the nervous tissues, midgut, gill, hepatopancreas, and ovary, while Sp ot/vpr-like were widespread in various tissues including the hepatopancreas, ovary, and hemocytes. In situ hybridisation revealed that Sp ot/vp-like mRNA was mainly detected in 6-9 ^th clusters in the cerebral ganglion, and oocytes and follicular cells in the ovary, while Sp ot/vpr-like was found to localise in F-cells in the hepatopancreas and oocytes in the ovary. In vitro experiment showed that the mRNA expression level of Sp vg in the hepatopancreas, Sp vgr in the ovary, and 17β-estradiol (E ₂ ) content in culture medium were significantly declined with the administration of synthetic Sp OT/VP-like peptide. Besides, after the injection of Sp OT/VP-like peptide, it led to the significantly reduced expression of Sp vg in the hepatopancreas and subduced E ₂ content in the haemolymph in the crabs. In brief, Sp OT/VP signaling system might inhibit vitellogenesis through neuroendocrine and autocrine/paracrine modes, which may be realised by inhibiting the release of E ₂ .
Competing Interests: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.