A New Species of genus Hemicorallium (Cnidaria: Octocorallia Scleralcyonacea Coralliidae) Collected from Okinawa Island

A new species of genus Hemicorallium (Coralliidae), Hemicorallium ryukyuense sp. nov., is described here. The specimen that was almost complete colony was found at a depth of 860 m, approximately 10 km east of Okinawa Island. The colony was identified by visual and microscopic observation of standard morphological characteristics (colony size, diameters of colony base and branches, diameter and height of autozooid mound, thickness of coenenchyme, sclerite sizes, etc.). The specimen has the larger (1.1-2.0 mm in diameter) autozooid mounds, as well as pinkish or reddish cortex and axis. The unique characteristics of the specimen are that it has no commensal burrows in the axis. This species is the first species of precious corals to have the Ryukyu Islands as its type locality. As well, molecular analysis is attempted to determine the phylogenetic relationship between this species and similar species. Although morphology clearly distinguished H. ryukyuense, the genome-wide analysis did not yield a definitive conclusion. The observed genetic distances among Hemicorallium species suggest H. ryukyuense may be a separate species. However, their phylogenetic relationships varied by locus, and genetic distances among Hemicorallium species remained smaller than genetic diversity those of within P. elatius and P. konojoi.