Octocoral Specimen Collection and Analysis

All specimens were collected around Oshima Island (31°31.35'N, 131°24.27'E) (Fig. 1), Miyazaki, Japan, by SCUBA diving and snorkeling. A small piece of tissue (5–10 mm) from each specimen was used for molecular analyses and the remainder was preserved in 99% ethanol for morphological analyses as reported by Koido et al. (2019) (link).
Specimens were previously deposited in Miyazaki University, Fisheries Sciences (MUFS) but were subsequently transferred and deposited at the Kuroshio Biological Research Foundation, Kochi, Japan (KBF) in the octocoral collection (OA). Morphological characteristics examined under a stereomicroscope included colony height, length and width of the stalk, presence of branches, length and width of polyps, length and width of tentacles, length and width of pinnules, number of rows of pinnules, and number of pinnules in the aboral row. Sclerites from polyps, and ones from the surface and interior of both stalk and branches of each specimen were examined. Sclerite shape, size, and microstructure were examined with light microscopy and scanning electron microscope (SEM) (HITACHI S-4800 and JEOL JSM-6500F).