First deep-sea Hamigera (Demospongiae: Porifera) species associated with Cold-Water Corals (CWC) on antipodal latitudes of the world. (October 2020) - Santín, Andreu
Abstract: Cold-water corals (CWC) are known to be deep-sea biodiversity hotspots, yet there is still a huge knowledge gap regarding their associated fauna. As so, CWC ecosystems pose as a perfect environment for the discovery of new species. In this context two new species of Hamigera (Demospongiae) have been recorded associated with CWC in antipodal parts of the world: Hamigera bibiloniae sp. nov. from the Blanes Canyon (north-western Mediterranean Sea) and Hamigera kellyae sp. nov. from the Clementsville Seamount (Macquire Ridge, New Zealand). Both species represent the first deep-sea records of the previously shallow-water restricted Hamigera, and mostly differ from other species in their huge spicule size, mostly doubling that of shallow-water congeneric species. Furthermore, the current geographical distribution of Hamigera, being only present in the Mediterranean and Pacific areas, might suggest a Tethyan affinity of H. bibiloniae sp. nov. proposing a potential role of deep-sea habitats as climatic refugees. Highlights: Two new species of Hamigera (Porifera) are here described from antipodal (Mediterranean vs. Pacific) parts of the world. They are the first deep-sea representatives for this previously shallow-exclusive genus, both occurring in association with Cold Water Corals. The similitudes between Hamigera (family Hymedesmiidae) and Lissodendoryx ( Lissodendoryx ) (family Coelosphaeridae) are discussed. Deep-sea ecosystems represent a unique environment for the discovery of new species. The sponge fauna associated with New Zealand's Cold Water Corals is still poorly studied compared with other areas of the world. The percentage of Mediterranean species with Tethyan ancestry might be more important than is currently known today.