Crustacean cardioactive peptide (CCAP) negatively regulates sand-diving behaviour in kuruma shrimp, Penaeus japonicus

Kuruma shrimp (Penaeus japonicus) exhibits sand-diving behaviour. The genetic control mechanism of this behaviour is still unclear, although previous single-cell transcriptome sequencing suggests that crustacean cardioactive peptide (CCAP) may be involved. In this study, we cloned the CCAP precursor cDNA (Pj-CCAP) in kuruma shrimp. It was predicted that the gene can be translated into four related peptides and one mature peptide (PFCNAFTGC-NH2), and is highly similar to crustaceans and insects. The predicted Pj-CCAP itself is highly conserved in other crustaceans. RT-qPCR and in situ hybridization analysis showed that Pj-CCAP was most highly expressed in muscle tissue. RNA interference and gene overexpression were used to assess the relationship between Pj-CCAP expression and sand-diving behaviour of shrimp. The results showed that at 6 h post-treatment, the sand-diving rate in the RNA interference group was significantly lower than that in the control group, while the heart rate of shrimp subjected to RNA interference was also significantly, but recovered to baseline levels within 12 h post-treatment. Overexpression resulted in a lower sand diving rate, and a transient increase in heart rate. The results suggest that Pj-CCAP is potentially a negative regulator of sand diving behaviour of kuruma shrimp, and may have an important role in regulating its physiological rhythms and behavioural patterns.