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Abstract

During larval settlement and metamorphosis, marine invertebrates undergo changes in habitat, morphology, behavior and physiology. How larvae co-ordinately regulate these changes is not well under- stood. Recently, we discovered a neuropeptide, myoinhibitory peptide (MIP), as an important regulator of larval settlement behavior in the marine annelid Platynereis dumerilii. MIP is a member of the ancient eumetazoan Wamide neuropeptide superfamily that includes insect al- latostatin B and Cnidarian GLWamides and is associated with life cycle transitions in many animal phyla. Here, we explore the contribution of MIP to feeding, another aspect of Platynereis life cycle progression. We find that MIP is expressed in both the brain and gut of developing Platynereis larvae. Activating MIP signaling by synthetic neuropepti- de addition causes increased gut peristalsis and pharynx extension. Conversely, morpholino knockdown of MIP expression delays the onset of feeding in Platynereis larvae. These results indicate that additional to its role in settlement, MIP is a regulator of Platynereis late larval and juvenile feeding and digestion. The dual roles of MIP in feeding and settlement may promote the coupling of these two processes during life history evolution. Through our integrative analysis of MIP function, we begin to establish Platynereis as a powerful model for studying the neuroendocrine regulation of feeding.