ABSTRACT
The last 20 years have shown a growing interest in developing non-conventional models for evo-devo purposes. In particular, the study of non-bilaterian metazoans offers the invaluable possibility to explore the origin of key bilaterian morpho-anatomical features, such as the presence of a head, a gut, a centralized nervous system and a mesoderm. Among non-bilaterian metazoans (i.e. Cnidaria, Placozoa, Ctenophora and Porifera), cnidarian models have been the best studied so far, and much work remains to understand the biology of the three other phyla. Porifera constitutes a monophyletic group of more than 9,300 species, split into four distinct classes: Demospongiae, Hexactinellida, Calcarea and Homoscleromorpha. The Homoscleromorpha class is of particular interest to study the evolution of animal epithelial features and two species of the Oscarella genus, Oscarella lobularis and Oscarella pearsei, are currently studied for evo-devo purposes. This chapter focuses on Oscarella lobularis, the type species of the genus Oscarella. The available resources (transcriptome, metagenome draft, well-described anatomy, histology, embryology, chemical fingerprints and so on) and mastered experimental tools (regenerative experiments, dissociated-cell reaggregation, in situ hybridization, fluorescent immunolocalization, cell death and proliferation assays, cell staining and tracking) make the Mediterranean homoscleromorph sponge Oscarella lobularis one of the best marine sponge models available so far.
