Hexacorals (Anthozoa: Actiniaria, Zoanthidea) from hydrothermal vents in the south-western Pacific

Four new species of sea anemones are described from the Eastern Lau Spreading Center, with notes on three additional Hexacorallia. Cyananthea hourdezi sp. nov. and Alvinactis chessi sp. nov. (Actinoscyphiidae) extend the range of the two previously monotypic, vent-endemic genera from the East Pacific Rise. Chondrophellia orangina sp. nov. (Hormathiidae) is the third species of its genus; it inhabits both hydrothermal vents and non-venting sites. Similarly, Sagartiogeton erythraios sp. nov. (Sagartiidae) was collected from non-vent settings, but is documented on video from near diffuse-flow hydrothermal vents. In addition, we report two species from families Actinostolidae and Hormathiidae whose identity could not be established based on the existing material, and provide a new record of a member of order Zoanthidea from a hydrothermal vent. The ecological context of the sites at the Eastern Lau Spreading Center containing sea anemones is described.