WHERE DOES THE MEDITERRANEAN-SEA BEGIN - ZOOGEOGRAPHICAL AFFINITIES OF THE LITTORAL SPONGES OF THE STRAITS-OF-GIBRALTAR

A geographical study of the littoral sponges from the Straits of Gibra ltar was undertaken, where the origin of these sponges is observed to be a transition between the different geographic regions that meet in the Straits. A great affinity was also observed between the Mauretania n fauna, the fauna from the Straits of Gibraltar and that from the ent ire Spanish Peninsular Mediterranean, thus conforming a very homogeneo us block within the group of areas studied. On the other hand, a numer ous group of species traditionally considered endemic to the Mediterra nean, such as: Haliclona mucosa, H. valliculata, H. cratera, H. fulva, H. aqueductus. H. mediterranea, Dendroxea lenis, Phorbas tenacior; He xadella racovitzai, Ircinia oros, Dictyonella incisa, Acanthella acuta , Diplastrella bistellata, etc. are believed to have an origin in trop ical or subtropical Alantic waters.