How diverse is sponge fauna in the Adriatic Sea?

The Adriatic Sea can be considered as a large, mostly shallow embayment of the Mediterranean Sea. The latitudinal SE-NW extension of the Adriatic results in considerable climate differences along its coast. In this work we compiled the listof sponges from classes Demospongiae and Homoscleromorpha recorded in the Adriatic up to now: we performed a thor-ough literature check and we added the results of our decade long research with a special emphasis on sponge fauna inmarine caves. All the records were assigned to the North, Middle or South Adriatic according to their geographic location,and the analysis showed a very high similarity among the sponge fauna of the 3 areas. The likeness between the N. andthe M. Adriatic is over 83 %, between the M. and the S. Adriatic over 76 % and between the N. and the S. Adriatic over66 %. Altogether 283 species of sponges from these two classes (our field data and literature survey) have been recordedin the whole Adriatic up to now, which is a considerably higher number than in previous reviews. Among the 125 speciesthat we found so far in our research along the Croatian coast, 77 were found in marine caves. We are still discovering spe-cies not previously found in the Adriatic Sea (especially from cryptic habitats) and here we report 15 new records for the Adriatic Sea, 9 of which were noted only in caves.