A new species and a new record of Cirratulidae (Annelida, Cirratulida) from Loki’s Castle vent field

Deep-sea research is a very active field in which environments such as hydrothermal vents are of particular interest because they host a unique and often endemic fauna. In this paper, we describe a new species of the genus Caulleriella Chamberlin, 1919 (Annelida, Cirratulidae Ryckholt, 1851) and report the presence of Raricirrus arcticus Buzhinskaja & Smirnov, 2017 at Loki’s Castle vent field (LCVF), which is the first detailed report of this species since the original description. Both species are illustrated and similarities with closely related species are discussed. We provide genetic data for COI, 16S and 28S for both species. Phylogenetic analyses confirm the identity of each species and the monophyly of each genus. Caulleriella jormungandri sp. nov., in addition to being common at LCVF, is recorded from stations without any known chemosynthesis-based environments, suggesting this species to be a part of the background fauna. Raricirrus arcticus was originally described from a cold seep, and with the new records from the Loki’s Castle hydrothermal vent, it is considered to be a specialist of chemosynthesis-based ecosystems and the geographic distribution of the species is vastly expanded from the Laptev Sea to the Nordic Seas.