Increasing knowledge of biodiversity on the Orphan Seamount: a new species of Tedania (Tedaniopsis) Dendy, 1924

English. A new Tedania species (Porifera) was collect using remotely operated vehicles duringthe Canadian mission HUD2010-029 and the British RRS Discovery Cruise DY081, onthe Orphan Seamount near the Orphan Knoll, northwest Atlantic, between 2999.88and 3450.4 m depth. Orphan Knoll is an isolated, drowned continental fragment550 km northeast Newfoundland in the Labrador Sea. This region is biologically richand complex and in 2007, the regional fisheries management organization operatingin the area regulated that no vessel shall engage in bottom-contact fishing activitiesuntil reviewed in 2020 with a review slated at the end of this year. Membersof the genus Tedania are uncommon in the temperate northern hemisphere withonly six species known previously: Tedania (Tedania) anhelans; Tedania (Tedania)pilarriosae; Tedania (Tedania) suctoria; Tedania (Tedania) urgorrii; Tedania (Tedaniopsis)gurjanovae; and Tedania (Tedaniopsis) phacellina. The particular features of the newsponge we describe are the very peculiar external morphology which is tree-like withdichotomous branching—a morphology not previously described in this subgenus; andthe combination of spicules found: long styles, the typical tornotes of the subgenusand two sizes of onychaetes. Additional information is provided on other species ofTedaniopsis described from the Atlantic Ocean. Based on the characteristics reported,we propose a new species, Tedania (Tedaniopsis) rappi sp. nov. in honor of Prof. HansTore Rapp (1972–2020), University of Bergen, Norway, a renowned sponge taxonomistand coordinator of the Horizon 2020 SponGES project. The holotype of T. (T.) phacellinaTopsent, 1912 from the Azores, the only other northern Atlantic species in the subgenusTedaniopsis, was reviewed for comparison.

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