Expression Characteristics and Potential Function of Neuropeptide MIP in Larval Settlement of the Echiuran Worm Urechis unicinctus

Larval settlement and metamorphosis are important developmental events in marine invertebrates.Some neuropeptides may play a key role in these processes.In this study,we revealed the expression characteristics of myoinhibitory peptide(MIP)in the embryos and larvae of the echiuran worm Urechis unicinctus using RT-qPCR,in situ hybridization and immunofluorescence techniques,and found its location in the top cells of the upper hemisphere was conservative in larvae.Furthermore,we used the active MIP peptide to verify its role in inducing the larval settlement of U.unicinctus,and confirmed that MIP can trigger an obvious larval settlement when 10μmol L^(−1) or 15μmol L^(−1) MIP was added in the seawater where early-segmentation larvae were cultured.Our finding indicated that neuropeptide MIP participates in the larval settlement in U.unicinctus.