. Ecological role and phylogenetic position of a new habitat-forming species (Canalipalpata, Sabellidae) from the Mediterranean mesophotic soft-bottoms
This study presents a description of Bispira riccardi sp. nov., a new habitat-forming sabellid polychaete from the
mesophotic NW Mediterranean Sea. Individuals, up to 20 cm long, show a peculiar morphology of radioles,
thoracic uncini, companion chaetae and ventral shield of the collar. The phylogenetic position of this new taxon
in the genus Bispira has been validated using nuclear (18S rRNA) and mitochondrial (COI) markers.
Aggregations of B. riccardi sp. nov. were found by ROV on horizontal muddy bottoms between 56 and 85 m, in
areas subjected to high trophic inputs. Patches are fragmented and dense (up to 943 individuals m 2) probably
accounting for various hectares. A 5-days continuous monitoring, carried out using an autonomous lander,
revealed that the contraction of the branchial crown was positively affected by temperature and current, rapidly
responding to meteorological events. The filtering activity and high density of these fields suggest a considerable
impact on the pelagic-benthic coupling and the amount of organic matter in the sediments. Indeed, meiofaunal
abundance and diversity within the aggregations resulted significantly higher than in outer stations. These
findings highlight the undisclosed potential of the deep Mediterranean Sea for sabellid diversity and their
importance as habitat-forming species on mesophotic soft bottoms