Porifera (Sponges): Recent Knowledge and New Perspectives
Résumé
Porifera, commonly named sponges, are true animals or metazoan despite their anatomical and morphological simplicity that had led to a long-time debate about their nature (animal versus vegetal) and constitution (colonies of unicellular organisms versus multicellular organisms). Sponges are a successful group of mostly marine filter feeder organisms that represent a major life form of several ecosystems. Devoid of organs, the main characteristics of their body plan are the presence of a network of pores (at the origin of their name), choanocyte chambers and canals devoted to water filtration and spicules (when present) allowing tissue physical support. Currently considered as the sister group to all the other animals, these organisms have a key phylogenetic position. Recent studies have shown that they possess an unexpected molecular complexity raising exciting questions about early animal evolution.