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.