Discovery of a new hydrothermal copepod from the Indian Ocean and proposal of Parabathyesola gen. nov. (Harpacticoida, Laophontidae, Esolinae).

Hydrothermal vent ecosystems are expected to harbor numerous meiobenthic animals; however, few studies have examined the species composition, abundance, and distribution of harpacticoid copepods in deep-sea hydrothermal assemblages. To gain insights into the natural biodiversity of such assemblages, we report a new species, Parabathyesola calida gen. et sp. nov. (subfamily Esolinae, family Laophontidae), from a deep-sea hydrothermal vent in the Onnuri Vent Field located on the Central Indian Ridge. This species can be considered a sister taxon of the monotypic genus Bathyesola Huys & Lee, 2000, sharing six derived character states in the antennules, maxillulary endopod, maxillipedal syncoxa, and thoracic legs in both sexes. However, it differs from Bathyesola in the combination of a female antennule with six segments and the first endopodal segment in the third and fourth legs with an inner seta, justifying the establishment of a new monotypic genus, Parabathyesola gen. nov. Therefore, the subfamily Esolinae now includes 19 species in nine genera. We also provide an amended dichotomous key to the genera of this subfamily.