Deep sponge communities of the Gulf of St Eufemia (Calabria, southern Tyrrhenian Sea), with description of two new species

Recently, the rich coral communities of the so called roche du large biocoenose of the Gulf of St Eufemia (southern Tyrrhenian Sea) between 90 and 130 m deep, have been described thanks to remotely operated vehicle (ROV) imaging. This preliminary survey evidenced the massive presence of a well-diversified sponge community living among the coral colonies. This work aims at giving an ecological overview of some of the dominant species of this environment, together with a taxonomic part including the description of new species: Topsentia calabrisellae sp. nov. and Haliclona (Soestella) fimbriata sp. nov. The silted, rocky outcrops of the Gulf of St Eufemia facilitate the settling mainly of massive sponges with erect habit which may also avoid sedimentation by growing on the coral colonies. On the other hand, the site Capo Vaticano, located at the southern boundary of the gulf, characterized by rocky boulders exposed to strong currents and completely devoid of corals, is inhabited by a poor megabenthic community, dominated by patches of massive sponges, such as Topsentia vaceleti, a species of recent description whose aspect in the field was still unknown. In the entire investigated area 19 species have been photographed (often for the first time in vivo), collected and identified, but the real sponge diversity is certainly under-estimated due to the difficulty of collecting all the sighted specimens through the ROV grabber. Similarly to the coral component, sponges also respond to the same environmental constraints by growing in heterogeneous patches or by showing different morphologies mainly associated with current and sedimentation conditions.