The Mediterranean mussel,Mytilus galloprovincialis, a novel model for developmental studies of mollusks

A model organism in developmental biology is defined by its experimental amenability as well as by resources created for the model system by the scientific community. For the most powerful models, the combination of both has already yielded a thorough understanding of development. However, the number of developmental model systems is still very limited, and their phylogenetic distribution is heavily biased. Members of one of the largest animal phyla, the mollusks, for example, have long been neglected as developmental model organisms. To remedy this shortcoming, we produced a detailed developmental transcriptome for the Mediterranean mussel Mytilus galloprovincialis , a bivalve mollusk, and expanded the list of experimental protocols available for this species. Our high-quality transcriptome allowed us to identify transcriptomic signatures of developmental transitions and to perform a first comparison with the Pacific oyster Crassostrea gigas that can be used in future multi-species analyses. To allow co-labelling studies, we optimized protocols for immunohistochemistry and hybridization chain reaction and combined both techniques to create high-resolution co-expression maps of developmental genes. The resources and protocols we describe here thus represent an enormous boost for the establishment of the Mediterranean mussel as a laboratory model in developmental biology. Summary statement Resources and techniques are described for the Mediterranean mussel Mytilus galloprovincialis , which, together, establish a novel model system for studying mollusk development and animal evolution.