Global diversity of sponges (Porifera: Spongillina) in freshwater

Porifera is a primarily marine phylum comprising more than 15,000 species. The successful and wide adaptive radiation of freshwater sponges (Haplosclerida: Spongillina) has resulted in the colonization of an extremely wide variety of habitats at all latitudes. Colonization is dated back to the Mesozoic, and the mono- or poly-phyletism of Spongillina, and the number of potential sponge invasions into freshwater is still under debate. Living freshwater sponges belong to 45 genera in six families for a total of 219 species. The highest diversity, at the scale of zoogeographic regions, is recorded from the Neotropical (65 species), Palaearctic (59 species), and Afrotropical regions (49 species). Endemic freshwater sponge species are 103 (47%) out of 219. All species belonging to the families Lubomirskiidae, Metschnikowiidae, and Malawispongiidae are endemic. Endemic species among the other families are 72% for Potamolepidae, 38% for Spongillidae, and 32% for Metaniidae. Data on some wide geographic areas are scattered and fragmentary if not almost completely lacking. Species richness is probably underestimated and doubtless destined to increase with further research.