Isolation of an Insulin-Like Receptor Involved in the Testicular Development of the Mud Crab .

Insulin-like androgenic gland hormone (IAG) is a key regulator of male sexual differentiation in crustaceans that plays important roles in secondary sexual characteristics and testicular development. As a hormone, IAG interacts with its membrane receptor to initiate downstream signal pathways to exert its biological functions. In this study, we isolated a full-length cDNA of an insulin-like receptor () from the mud crab . Sequence analysis revealed that this receptor consists of a Fu domain, two L domains, three FN-III domains, a transmembrane domain, and a tyrosine kinase domain, classifying it as a member of the tyrosine kinase insulin-like receptors family. Our results also suggested that was highly expressed in the testis and AG in males. Its expression in the testis peaked in stage I but significantly decreased in stages II and III ( < 0.01). Next, both short- and long-term RNA interference (RNAi) experiments were performed on males in stage I to explore -IR function in mud crabs. The results showed that and expression levels in the testis were significantly down-regulated after the specific knockdown of by RNAi. Additionally, the long-term knockdown of led to a considerable decrease in the volume of seminiferous tubules, accompanied by large vacuoles and a reduced production of secondary spermatocytes and spermatids. In conclusion, our results indicated that is involved in testicular development and plays a crucial role in transitioning from primary to secondary spermatocytes. This study provided a molecular basis for the subsequent analysis of the mechanism on male sexual differentiation in Brachyuran crabs.