New Insights into the Biodiversity of Benthic Hydroids (Cnidaria, Hydrozoa) from Seamounts in the Remote Macquarie Ridge, with the Description of Three New Species.

The Macquarie Ridge is a major seafloor feature in the Southern Hemisphere between New Zealand and the Antarctic continent, and its marine communities have been poorly explored. During the MacRidge 2 TAN0803 survey conducted on board the R/V Tangaroa, several seamounts of the Macquarie Ridge were sampled. Among the benthic samples obtained, a collection of hydroids was present. Eleven species were recorded, including Acryptolaria seamountensis sp. nov., Filellum liberum sp. nov. and Nemertesia macquariensis sp. nov. Anthoathecata is represented only by Eudendrium sp. The collection is essentially dominated by Leptothecata, with ten species, belonging to the families Campanulariidae, Lafoeidae, Phylactothecidae, Plumulariidae and Sertularellidae. Lafoeidae is by far the most diversified family, accounting for half of the leptothecate species. At the generic level, the collection is dominated by the deep-water genus Acryptolaria, with four species; all the remaining genera are represented by a single species. Seven species represent new records for the area and Calamphora quadrispinosa Watson, 2003 is recorded for the second time.