Fast Cycling Culture of the Marine Annelid Platynereis dumerilii

Abstract

Platynereis dumerilii, a marine annelid, is a model animal that has gained popularity in various fields such as developmental biology, biological rhythms, nervous system organization and physiology, behaviour, reproductive biology, and epigenetic regulation. The transparency of P. dumerilii tissues at all developmental stages makes it easy to perform live microscopic imaging of all cell types. In addition, the slow-evolving genome of P. dumerilii and its phylogenetic position as a representative of the vast branch of Lophotrochozoans add to its evolutionary significance. Although P. dumerilii is amenable to transgenesis and CRISPR-Cas9 knockouts, its relatively long and indefinite life cycle, as well as its semelparous reproduction have been hindrances to its adoption as a reverse genetics model. To overcome this limitation, an adapted culturing method has been developed allowing much faster life cycling, with median reproductive age at 15 weeks instead of 6-8 months using the traditional protocol. A low worm density in boxes and a strictly controlled feeding regime are important factors for the rapid growth and health of the worms. Moreover, a genetic selection for fast-reproducing individuals has been applied to isolate a "Fast Forward" strain that can be used for egg microinjection. This culture method has several advantages, such as being much more compact, not requiring air bubbling or an artificial moonlight regime for synchronized sexual maturation, and necessitating only limited water change. A full protocol for worm care and handling is provided.