Expression analysis of the insulin-like peptides genes (ILPs) in the redclaw crayfish <i>Cherax quadricarinatus</i> and new insights into sexual development

Insulin-like peptides (ILPs) are involved in various physiological processes in metazoans, including metabolism, growth, and reproduction. However, their presence and function in decapods are largely unexplored. To investigate the role of ILPs in the redclaw crayfish, this study characterized two ILP genes (Cq-ILP1 and Cq-ILP2) and analyzed their genomic structure and protein domains. Multiple sequence alignments revealed highly conserved structural features across ILPs from different species. Tissue expression analysis indicated that Cq-ILP1 was exclusively expressed in the ovary, suggesting its involvement in female reproduction. In early juvenile stages, Cq-ILP1 expression was first detected in female individuals at 2 cm body length (BL2), coinciding with the appearance of genital pores. Additionally, Cq-ILP1 expression progressively increased during ovarian development stages from I to V, then decreased to its lowest level at the end of stage VI. These findings suggested that Cq-ILP1 played a pivotal role in sexual development. Moreover, injection of Cq-ILP1–dsRNA resulted in a significant reduction in vg expression. These results provided new insights into the function of non-IAG ILP genes and offered valuable resources for future research on ovarian development in crustaceans.