Evaluation of the Effect of Adipokinetic Hormone/Corazonin-Related Peptide (ACP) on Ovarian Development in the Mud Crab, Scylla paramamosain

In this study, we identified Sp-ACP and its putative receptor from the mud crab S. paramamosain and explored its potential role in ovarian development. RT-PCR results suggested Sp-ACP was extensively expressed in nervous tissues, the ovary, the middle gut, and the Y-organ, while Sp-ACPR was highly expressed in the ovary. The expression level of Sp-ACP in the ovary, eyestalk, and cerebral ganglia gradually increased during ovarian development, whereas its receptor exhibited an opposite expression pattern in the ovary. Immunofluorescence revealed that ACP was specifically localized in the follicle cells of the ovary. In vitro experiments showed that the expression of vitellogenin receptor (Sp-VgR) in the ovary was significantly increased by 4 and 6 h incubation of Sp-ACP (10 nM). In addition, 12 h injection of Sp-ACP significantly induced the levels of Sp-Vg in the hepatopancreas and Sp-VgR in the ovary, and hemolymph 17 beta-estradiol titer. Finally, it demonstrated that prolonged injection of Sp-ACP significantly increased the level of Vg and VgR expression, hemolymph 17 beta-estradiol titer, GSI, and the oocyte diameter. In conclusion, our results suggested that ACP is involved in the regulation of ovarian development of S. paramamosain, likely by inducing hepatopancreas Sp-Vg expression through estradiol and promoting the uptake of Vg by oocytes.