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A new genus and species of axiid shrimp, Carolinaxius kexuae gen. et sp. nov. is described and illustrated based on a single specimen collected from an unnamed seamount in the Caroline Ridge, northwest Pacific. Although both chelipeds are missing, the specimen can be distinguished from other axiid genera by a combination of characteristics: narrowly triangular rostrum; median carina and lateral gastric carina each with one prominent tooth; submedian gastric carinae converging posteriorly, with teeth; cornea weakly pigmented, eyestalk with acute distomesial tooth on dorsal surface; male pleopod 1 two-articled; pleopod 2 with appendix interna and appendix masculina; pleopods 3–5 with appendix interna. The molecular phylogeny suggests the new genus is most closely related to another recently described genus living inside hexactinellid sponges on seamounts in the Indian Ocean, Montanaxius Dworschak, 2016. However, it differs from Montanaxius in the shape of the rostrum, the arrangement of teeth on the carapace, and the shape of the eyestalk. Besides, the significant molecular differences support the two belonging to different genera. [ABSTRACT FROM AUTHOR]

Three deep-sea black corals belonging to the family Schizopathidae, are reported from two seamounts on the Caroline Ridge in the tropical Western Pacific: Umbellapathes parva sp. nov. with depth of 1 488–1 766 m, Telopathes cf. magna MacIsaac & Best, 2013 with depth of 937–1 016 m, and Stauropathes cf. punctata (Roule, 1905) with depth of 942–1 353 m. The latter two species are the first records in the Western Pacific Ocean. U. parva sp. nov. is characterized by monopodial corallum, relatively long unpinnulated stalk with complex pinnulated branches developing from the lowermost primary pinnules and small spines. It differs from two known congeners by much smaller spines and the present of secondary pinnules. T. cf. magna MacIsaac & Best, 2013 has sparsely branched corallum, relatively long and simple pinnules arranged in subopposite or alternate pairs. S. cf. punctata (Roule, 1905) is characterized by the corallum with almost planar pinnulated branches, and pinnules arranged in subopposite pairs. Our results indicate that the corallum size and shape are variable in conspecific specimens particularly those at different growth stages. By contrast, the size of the polypar spines as well as the abpolypar spines have little variation and can be served as a main differing feature for schizopathid species. The phylogenetic analyses using nuclear internal transcribed spacer region (spanning partial 18S rDNA, ITS1, 5.8S, ITS2, and partial 28S rDNA) and two mitochondrial fragments cox3-IGR-cox1 (COI) and trnW-IGR-nad2 (NAD2) showed Telopathes, Stauropathes, and Bathypathes had close relationships, and Umbellapathes formed a sister clade with Alternatipathes. [ABSTRACT FROM AUTHOR]

Two new species of Chrysogorgia Duchassaing & Michelotti, 1864 collected from the Caroline seamounts in the tropical Western Pacific Ocean are described. Chrysogorgia pinniformis sp. nov. belongs to Versluys' group C (Squamosae typicae) with only scales in polyp body wall and tentacles. C. pinniformis sp. nov. is characterized by large branches pinnately branched and forming multiple fans with its small branches regularly and quasi-dichotomous branched, and scales and rods present in the polyp mouth area. It is most similar to C. pinnata Cairns, 2007 by the pinnate trait, but differs from the latter by its group C pattern (vs. group A, Spiculosae) and having sclerites present in the polyp mouth area (vs. absent). Chrysogorgia varians sp. nov. belongs to the Chrysogorgia group A (Spiculosae) with rods distributed in the polyp body wall and tentacles. It is characterized by warty rods and elongated scales in the tentacles, many warts and ridges on the scales, conspicuously toothed margins at the rounded ends in the pinnules, and small rods with ridge-like warts in the polyp mouth area. This species was frequent and abundant in the Caroline seamounts during our cruises and its morphological variability in growth period was obvious. The phylogenetic analyses based on mtMutS and 28S rDNA regions supported the assignment of the new species to the genus Chrysogorgia. However, the mtMutS marker showed very limited usefulness for species delimitation and inner relationship inference of Chrysogorgia. In contrast, the 28S rDNA showed much higher level of genetic variation, and it may be a potential barcode for this genus. In the 28S rDNA trees, the two new species clustered together. Additionally, compilation of our data showed that 42 of 78 (ca. 54%) Chrysogorgia species were found in the Indo-West Pacific convergent region, indicating that this area may be a hotspot of deep-water Chrysogorgia species. [ABSTRACT FROM AUTHOR]