Cheon Young Chang

Occurrence of the newly described kinorhynch genus Meristoderes (Cyclorhagida: Echinoderidae) in Korea, with the description of four new species

Meristoderes is the most recently described kinorhynch genus and has until now only accommodated its type species M. macracanthus from the Mediterranean and M. galatheae from the Solomon Islands in Southeast Asia. The present contribution is an account on the genus based on samples from the ongoing exploration of the kinorhynch fauna in coastal and subtidal waters around in the Korean Peninsula. The samples yielded no less than five new species of Meristoderes, of which four are formally described herein, whereas only diagnostic notes are provided for the fifth. The descriptions are supplemented with a key to species of the genus, and morphological notes on the organization of cephalic structures and cuticular trunk structures. New morphological findings include intrageneric variation in the composition of the terminal segment, which may have either one unpaired or two paired tergal plates. The data also show that the differentiation of a tergal and sternal plate in segment 2 varies greatly between the species. Results of the present study indicate that the genus probably holds a significant, unrecovered biodiversity, but the data also shed light on potential future taxonomic problems among genera of Echinoderidae and stress the importance of identifying additional diagnostic traits to define Meristoderes.

Two New Marine Gastrotrichs of the Genus Ptychostomella (Macrodasyida, Thaumastodermatidae) from South Korea

Abstract Two new thaumastodermatid gastrotrichs belonging to the genus Ptychostomella are described from the shallow sublittoral sand bottom in the eastern coast of South Korea. In having the embossed cuticular armature, Ptychostomella orientalis n. sp. is most allied to P. lepidota Clausen, 2000, the only congeneric species so far known as possessing such a cuticular armature. Ptychostomella papillata n. sp. is characterized by the terrace-shaped cuticular protrusion on head region, and the numerous papillae with sensory hair(s). Description of the two new species is prepared with a character comparison table and a key to the species of Ptychostomella. This is the first record of genus Ptychostomella from the North Pacific.

Pseudostomella gastrotrichs (Macrodasyida, Thaumastodemiatidae) from South Korea with a brief review of the Genus

Two new marine gastrotrichs of the genus Pseudostomella, P. longifurca and P. koreana, are described from the shallow sublittoral sand bottoms of South Korea. Pseudostomella longifurca n. sp. is characterized by the cuticular armature with tetrancres, five dorsal papillae on the prebuccal apparatus, four dorsolateral adhesive tubes, and elongated pedicle. Pseudostomella koreana n. sp. is distinguished from its congeners by the small body, tetrancres, two pairs of dorsolateral adhesive tubes, and tube‐shaped copulatory organ. A brief review of the genus is prepared, with the character comparison table for all congeners currently recognized, and a revised key to the species of Pseudostomella. This is the first record of the genus Pseudostomella from East Asia.

TWO NEW SPECIES OF THAUMASTODERMA (GASTROTRICHA, MACRODASYIDA) FROM KOREA

Abstract Two new marine gastrotrichs of the genus Thaumastoderma are described from South Korea T. coronarium sp. nov. was collected from the intertidal zones of Manripo beach and Sopori, Tokchok Island in the Yellow Sea. This species seems to be most closely related to T. bifurcatum CLAUSEN, 1991 or T. truncatum CLAUSEN, 1991 in that they share the following characteristics: one pair of simple, spatulate tentacles; six pairs of dorsal cirri; and absence of eye spots. It differs from these species in having four conspicuous head papillae and a different arrangement of dorsal cirri. T. appendiculatum sp. nov. was collected from the intertidal and shallow sublittoral zones of Pong po beach, Sokcho in the East Sea of Korea, and is easily distinguished from its congeners in having a pair of stout adhesive tubes on the posterior trunk margin, and in that it frequently possesses accessory dorsal cirri. This is the first report on marine gastrotrichs from Korea, and the first record of the genus Thaumastoderma i...

Description of two new thaumastodermatids (gastrotricha, macrodasyida) from Korea

Two new marine gastrotrichs of the family Thaumastodermatidae are described from South Korea. Tetranchyroderma gracilium n. sp. bears pestle organs, tetrancres, and two pairs of large dorsolateral tubes. It seems most closely related to T. massiliense Swedmark, T. heterotubulatum Hummon, Todaro and Tongiorgi, and T. boreale Clausen. Thaumastoderma copiophorum n. sp. has five pairs of dorsal cirrata, the overall picture of which differs clearly from that of all known species. In the presence of accessory cirrata, it relates to T. appendiculatum Chang, Lee and Clausen

Brackish-water Copepods of the Family Tachidiidae(Copepoda: Harpacticoida) from South Korea

Four harpacticoid species belonging to the family Tachidiidae are reported from the coastal waters and salt marshes in South Korea: Tachidius discipes Giesbrecht, 1881, Neotachidius parvus Huys, Ohtsuka, Conroy-Dalton and Kikuchi, 2005, Microarthridion litospinatus Shen and Tai, 1973 and Geeopsis incisipes(Klie, 1913). The latter two species and genera are new to Korean fauna. The previous record of T. discipes reported by Song and Chang(1995)from Korea is affirmed by the finding of male specimens. Microarthridion litospinatus is first known outside the type locality, and redescribed herein in detail. A key to the five species and four genera of the family Tachidiidae hitherto known from South Korea is presented.

Complete Mitochondrial Genomes of Carcinoscorpius rotundicauda and Tachypleus tridentatus (Xiphosura, Arthropoda) and Implications for Chelicerate Phylogenetic Studies

Horseshoe crabs (order Xiphosura) are often referred to as an ancient order of marine chelicerates and have been considered as keystone taxa for the understanding of chelicerate evolution. However, the mitochondrial genome of this order is only available from a single species, Limulus polyphemus. In the present study, we analyzed the complete mitochondrial genomes from two Asian horseshoe crabs, Carcinoscorpius rotundicauda and Tachypleus tridentatus to offer novel data for the evolutionary relationship within Xiphosura and their position in the chelicerate phylogeny. The mitochondrial genomes of C. rotundicauda (15,033 bp) and T. tridentatus (15,006 bp) encode 13 protein-coding genes, two ribosomal RNA (rRNA) genes, and 22 transfer RNA (tRNA) genes. Overall sequences and genome structure of two Asian species were highly similar to that of Limulus polyphemus, though clear differences among three were found in the stem-loop structure of the putative control region. In the phylogenetic analysis with complete mitochondrial genomes of 43 chelicerate species, C. rotundicauda and T. tridentatus were recovered as a monophyly, while L. polyphemus solely formed an independent clade. Xiphosuran species were placed at the basal root of the tree, and major other chelicerate taxa were clustered in a single monophyly, clearly confirming that horseshoe crabs composed an ancestral taxon among chelicerates. By contrast, the phylogenetic tree without the information of Asian horseshoe crabs did not support monophyletic clustering of other chelicerates. In conclusion, our analyses may provide more robust and reliable perspective on the study of evolutionary history for chelicerates than earlier analyses with a single Atlantic species.

Two Harpacticoid species of genera Nitokra and Ameira (Harpacticoida: Ameiridae) from brackish waters in Korea

Abstract A new species of Nitokra and Ameira parvula (Claus) belonging to the family Ameiridae are recorded from brackish waters in South Korea. Nitokra koreanus n. sp. most resembles N. spinipes and N. pietschmanni, however, it is characteristic in having the character combination of ellipsoidal P5 exopod and very short P1 enp 1. Ameira parvula is reported for the first time from the Northwestern Pacific. Description of the new species and the taxonomic accounts of both species are presented.

Two new species of harpacticoid copepods from anchialine caves in karst area of North Vietnam

Two new harpacticoid species belonging to the genera Microarthridion Lang, 1944 (Tachidiidae) and Nitocra Boeck, 1864 (Ameiridae) are recorded from underground caves in the karst area of Ninh Binh Province, North Vietnam. Microarthridion thanhi n. sp. is distinguished from congeneric species by the number of setae on the antennary exopod, the structure of leg 5 in both sexes, and the finger-like process modified from an outer distal pinnate seta of the third endopodal segment of leg 2 in the male. Nitocra vietnamensis n. sp. has the character combination of six setae on the ellipsoidal exopod of leg 5 in both sexes, the first endopodal segment of leg 1 shorter than the whole exopod, the seta/spine armature of an inner seta of P2-P4 enp-1 and four elements on P2 enp-3, and the reduction of the proximal endite to a seta on the maxillary syncoxa.

DNA Barcoding of Metazoan Zooplankton Copepods from South Korea.

Copepods, small aquatic crustaceans, are the most abundant metazoan zooplankton and outnumber every other group of multicellular animals on earth. In spite of ecological and biological importance in aquatic environment, their morphological plasticity, originated from their various lifestyles and their incomparable capacity to adapt to a variety of environments, has made the identification of species challenging, even for expert taxonomists. Molecular approaches to species identification have allowed rapid detection, discrimination, and identification of cryptic or sibling species based on DNA sequence data. We examined sequence variation of a partial mitochondrial cytochrome C oxidase I gene (COI) from 133 copepod individuals collected from the Korean Peninsula, in order to identify and discriminate 94 copepod species covering six copepod orders of Calanoida, Cyclopoida, Harpacticoida, Monstrilloida, Poecilostomatoida and Siphonostomatoida. The results showed that there exists a clear gap with ca. 20 fold difference between the averages of within-specific sequence divergence (2.42%) and that of between-specific sequence divergence (42.79%) in COI, suggesting the plausible utility of this gene in delimitating copepod species. The results showed, with the COI barcoding data among 94 copepod species, that a copepod species could be distinguished from the others very clearly, only with four exceptions as followings: Mesocyclops dissimilis–Mesocyclops pehpeiensis (0.26% K2P distance in percent) and Oithona davisae–Oithona similis (1.1%) in Cyclopoida, Ostrincola japonica–Pseudomyicola spinosus (1.5%) in Poecilostomatoida, and Hatschekia japonica–Caligus quadratus (5.2%) in Siphonostomatoida. Thus, it strongly indicated that COI may be a useful tool in identifying various copepod species and make an initial progress toward the construction of a comprehensive DNA barcode database for copepods inhabiting the Korean Peninsula.