A review of the Mediterranean Sea sponge biogeography with, in appendix, a list of the demosponges hitherto recorded from this sea.

The total number of porifera species hitherto recorded from the Mediterranean Sea is 649. Demospongiae are 597, Calcarea 44, Hexactinellida 8. The demosponge distribution, studied on fifteen Mediterranean zones is not uniform, even if not proportional to the number of taxonomic studies performed in each area. The highest faunistic affinities are among the southern and eastern parts of the basin, where seawater temperature is relatively warmer. The present day Mediterranean demosponge fauna is formed by a large nucleus of endemic species (48,2 %), by cold water (19,8 %), temperate (12 %) and warm water (5,7 %) species. Cosmopolitan species (9,3 %) are probably over estimated, whereas few species migrated from the Red Sea. The present day composition and biotic affinity of the Mediterranean sponge fauna can be explained, at some extent, by the geological history of this basin. Most of the paleomediterranean fauna did not survive the messinian salinity crisis but a small number of possible Tethyan relics. The demosponge list in appendix is updated according to the Systema Porifera, the revision of all the extant sponge genera published in October 2002.