Molecular Phylogeny and Taxonomy of the Coral Genus Cyphastrea (Cnidaria, Scleractinia, Merulinidae) in Japan, With the First Records of Two Species.

The scleractinian coral genus Cyphastrea is widely distributed in the Indo-Pacific region and is common from the subtropical to the warm-temperate regions in Japan. Three new species in this genus have recently been reported from south-eastern Australia or the Red Sea. However, taxonomic and species diversity have been little studied so far in Japan. In this study, we analyzed 112 specimens of Cyphastrea collected from the subtropical to the warm-temperate regions in Japan to clarify the species diversity in the country. This analysis was based on skeletal morphological and molecular analyses using three genetic markers of the nuclear 28S rDNA, histone H3 gene, and the mitochondrial noncoding intergenic region between COI and tRNAmet. The molecular phylogenetic trees showed that our specimens are separated mainly into four clades. Considering the morphological data with the molecular phylogenetic relationships, we confirmed a total of nine species, including two species, C. magna and C. salae, recorded for the first time in Japan. Although eight out of nine species were genetically included within Cyphastrea, one species, C. agassizi, was genetically distant from all other species and was closely related to the genus Leptastrea, suggesting the return of this species to the genus to which it was originally ascribed. Two newly recorded species were reciprocally monophyletic, while the other six species (excluding C. agassizi) clustered in two clades without forming species-specific lineages, including three polyphyletic species. Thus, the species boundary between species in Cyphastrea remains unclear in most species using these three sequenced loci.

Transplantation Tests of Precious Coral Fragments Using Small-sized Artificial Substratum.

Since the Roman era, precious corals have been used to make ornaments worldwide, and their demand has recently increased. As a basic study for artificial cultivation, we transplanted Corallium japonicum fragments. In 2016 and 2017, 132 fragments approximately 3-5 cm in length were attached to small-sized artificial substratums using marine epoxy on land. These artificial substratums, acting as transplant substrates, were then transported and sunk to a depth approximately 100 m off the coast of Otsuki Town and Tosashimizu City, Kochi Prefecture, where precious corals once flourished. From six months to three years post-submersion, we successfully recovered the transplanted substrates and found a total of 107 fragments (81%). We confirmed that 106 of these fragments were alive 177 to 936 days after transplantation. Although we could not measure growth rates due to the initial damage caused by the transplantation, we observed growth in coenenchyme tissues, new polyps and new branches in the 104 surviving fragments. This result suggests there is great potential to artificially multiply precious corals, which could aid in the development of a sustainable precious coral industry.