Sponge (Oscarella carmela) 

Sponges of the phylum Porifera represent some of the most primitive animal species, occupying a unique evolutionary position on the cusp of the development of multicellularity. Sponges are multicellular organisms, with a body plan organized around the flow of water through the organism. In forming the pores through which the water flows, sponges have cells with differing specialized functions. However, they do not display a tissue level of organization. Interestingly, any individual cell of a sponge is capable of regenerating the entire organism.

Oscarella carmela is a member of a small unique subclass of sponges call the homoscleromorpha. These sponges are characterized by several features which blur the line between sponges and the eumetazoa, the true animals. Most notably, the larvae of homoscleromorphs contain cells which display many tissue-like characteristics. As such, O. carmela is an ideal organism in which to study the evolutionary origins of early animals and multicellularity.

Though its genome has not been sequenced, other comparative genomics approaches have been used to study O. carmela. Researchers at CIG have analyzed ESTs (Expressed Sequence Tags), gene fragments from the set of actively expressed genes. In doing so, they found that genes from many of the signaling pathways used by animals during development are also present in O. carmela. Further analysis of these genes will hopefully shed light on the genomic changes which occurred during the evolution of multicellularity.