Sung-Jin Hwang

A New Species of Genus Coeloplana (Ctenophora: Tentaculata: Platyctenida) from Korea

Since November, 2006, the new creeping platyctenid ctenophore, Coeloplana anthostella n. sp., has been collected from twigs and polyp masses of encrusting dendronephthyans at a depth of 26-32 m off the coast of Munseom, Jejudo Island. This new species is distinguished from C. bocki Komai, 1920 and C. komai Utinomi, 1963 by its smaller size, the absence of dorsal papillae, and the deep scarlet colored star-shaped markings on the dorsal plane. This novel addition to ctenophore fauna is presently described and illustrated in detail.

New Records of Creeping Ctenophores, Genus Coeloplana (Tentaculata: Platyctenida: Coeloplanidae), from Korea

Creeping ctenophores, Coeloplana species, were collected by SCUBA divers throughout the year (November 2006 to June 2010) from the branches and polyp masses of encrusting dendronephthyas at a depth of 20-32m off Munseom Island (Seogwipo-si, Jeju-do, Korea). A single individual of a newly recorded species in Korea, Coeloplana bocki Komai, 1920, was collected together with C. anthostella from the same location on 16 August 2009. A large number of individuals of each species were subsequently collected from the host Dendronephthya aff. dendritica on 20 June 2010. C. bocki can be distinguished from C. anthostella Song and Hwang, 2010 and C. komaii Utinomi, 1963 by its unique blue and orange colored stripes, and/or the branching and anastomosing milky-white stripes encircling the aboral sense organ towards the margin. The detailed morphology and molecular sequence information (nuclear 18S rDNA, internal transcribed spacer 1, and mitochondrial cox1 gene sequences) for C. bocki is provided, and C. bocki and C. anthostella are compared.

Four New Records of Dendronephthya Species (Octocorallia: Alcyonacea: Nephtheidae) from Korea

Soft corals were collected from the subtidal zone in the coastal regions of Jejudo Island between 1975 and 2010. By the taxonomic work on them, three species in the subgenus Dendronephthya (Dendronephthya) and one species in the subgenus Dendronephthya (Roxasia) of family Nephtheidae were newly added to Korean fauna: Dendronephthya (Dendronephthya) aurea Utinomi, 1952, Dendronephthya (D.) koellikeri Kukenthal, 1905, Dendronephthya (D.) mucronata (Putter, 1900), and Dendronephthya (Roxasia) decussatospinosa Utinomi, 1952. These species are mainly distributed on the rocky substratum at the southern coast from 10 and 32 m. As a result of this study hirteen species in the genus Dendronephthya have been reported from Korean waters until now.

Taxonomic Study of Suborder Calcaxonia (Alcyonacea: Octocorallia: Anthozoa) from King Sejong Station, Antarctic

Some gorgonians in the families, Primnoidae and Isididae within the suborder Calcaxonia were collected from subtidal zones between depths of 10 and 45 m in the coastal regions of King Sejong Station (62°13′S, 058° 47′W), Korea Polar Research Institute of Korea Ocean Research and Development Institute (KORDI) by SCUBA diving from 2009 to 2011. Three species in the Primnoidae, Arntzia gracilis (Molander, 1929), Thouarella (Thouarella) antarctica (Valenciennes, 1846) and Onogorgia nodosa (Molander, 1929), and also one species in the family Isididae, Tenuisis microspiculata (Molander, 1929) are newly recorded to octocorallian fauna in Marian Cove and Potter Cove of King George Island. These four species have been described in detail.

First Record of One Sessile Ctenophora, Lyrocteis imperatoris, and Its Embryos form Korea

The sessile ctenophores, Lyrocteis imperatoris Komai, 1941 were collected for the first time from Garinyeo, offshore Seogwipo of Jejudo Island by SCUBA diving on June 18, 2009. This species distributed in West North Pacific was newly recorded in Korean waters. Its embryos in various developmental stages were observed in the internal brood chamber.

Sexual reproduction of the soft coral Dendronephthya castanea (Alcyonacea: Nephtheidae)

Abstract Dendronephthya castanea Utinomi, 1952 is a member of the family Nephtheidae, and dominates shallow waters adjacent to the southern part of Jejudo Island, Korea. This species is a gonochoric internal brooder with a sex ratio of 1:1, and releases planulae around the time of the full and new moon from July to September, when the seawater temperature peaks. The gametogenic cycle is annual, and oogenesis (12 months) is longer than spermatogenesis (4–5 months). No difference in reproductive features including sexuality, sex ratio, gametogenesis and gametogenic cycles was found between the sympatric species D. castanea and D. gigantea, and there was no temporal reproductive isolation. Investigation of the morphological taxonomy and molecular biology of these species indicates that they have very similar or identical traits, suggesting an absence of speciation and a need for taxonomic reclassification.

Geographical variations in bacterial communities associated with soft coral Scleronephthya gracillimum

Environmental impacts can alter relationships between a coral and its symbiotic microbial community. Furthermore, changes in the microbial community associated with increased seawater temperatures can cause opportunistic infections, coral disease and death. Interactions between soft corals and their associated microbes are not well understood. The species Scleronephthya gracillimum is distributed in tropical to temperate zones in coral assemblages along the Kuroshio Current region. In this study we collected S. gracillimum from various sites at different latitudes, and compared composition of their bacterial communities using Next Generation Sequencing. Coral samples from six geographically distinct areas (two sites each in Taiwan, Japan, and Korea) had considerable variation in their associated bacterial communities and diversity. Endozoicimonaceae was the dominant group in corals from Korea and Japan, whereas Mycoplasma was dominant in corals from Taiwan corals. Interestingly, the latter corals had lower relative abundance of Endozoicimonaceae, but greater diversity. These biogeographic differences in bacterial composition may have been due to varying environmental conditions among study locations, or because of host responses to prevailing environmental conditions. This study provided a baseline for future studies of soft coral microbiomes, and assessment of functions of host metabolites and soft coral holobionts.

New Records of Endocoelantheainea and Nynantheae (Anthozoa: Zoantharia: Actiniaria) from Korea

Actiniarians were collected from the rocks and sand bed of Jejudo Island, Ulleungdo Island, and Wangdolcho in Korean waters from 2004 to 2009. They were classified as two species of two families belonging to the suborders Endocoelantheainea and Nynantheae. Especially, suborder Endocoelantheainea, with distinct development of mesenteries, was firstly added to Korean athenarian fauna with the species, Halcurias carlgreni McMurrich, 1901. Calliactis polypus (Forskal, 1775) showing the commensalism with hermit crab, was easily distinguished from C. japonica by external features and the composition of cnidae. These two species were described in detail with tables and figures.