Deep sea molluscan fauna of the Cretan Sea (Eastern Mediterranean): Faunal, ecological and zoogeographical remarks

Abstract

The deep sea molluscan fauna of the Cretan Sea (Eastern Mediterranean) was investigated from living material collected by the R/Vs“AEGAEO” and“PHILIA” cruises in the framework of the MTP/MAST EU research programme CINCS, carried out by the I.M.B.C. Examination of the deep sea benthos, with particular reference to the phylum Mollusca, over a grid of stations from depths between 40 and 1570 m, revealed the presence in the area of a diverse fauna consisting of 147 species belonging to 6 different classes. Large numbers of species (44) are new elements of the molluscan fauna of the Cretan Sea while another 4 species (1 Polyplacophora, 2 Gastropoda, and 1 Bivalvia) have not been reported so far from the Aegean or the Eastern Mediterranean. The majority of the species exhibit a wide bathymetrie distribution, from the continental shelf region to the bathyal slope, and only a few species are considered as deep sea species (reported only from the latter). The faunal composition of the collected material from the studied area (in depths over 200 m) clearly demonstrates the presence in the Cretan Sea of theAbra longicallus-association, already reported in other deep basins of the Mediterranean where similar research has been carried out. However, the presence of the bivalveNuculoma aegeensis even in the shallow waters of the continental shelf strengthens the opinion of other authors (Janssen 1989;Dounas &Koukouras 1992) that theNuculoma aegeensis “facies” of the above association is not found as deep asdi Geronimo (1974) had claimed (1500 m). Most of the deep sea mollusc species collected from the Cretan Sea are distributed from the Mediterranean to the Atlanto-Mediterranean and Boreal province while no species with an Indo-Pacific origin (Lessepsian immigrants) were found. Taking into consideration results of studies on the molluscan fauna from shallow waters of the Cretan Sea (Koutsoubas et al. 1992) it can be concluded that this part of the Mediterranean could not be considered as an impoverished system, as it hosts a rather enriched and diverse molluscan fauna numbering more than 400 species.