Two new species of non-marine Ostracoda (Crustacea) of the genera Vestalenula Rossetti amp; Martens, 1998 (Darwinuloidea) and Microloxoconcha Hartmann, 1954 (Cytheroidea) from Tsushima, Japan, and a summary of the non-marine ostracod fauna of the island.

The archipelago of Tsushima is located in the Korea Strait, at the southern end of the Sea of Japan (East Sea), and lies almost equidistant from Korea and Japan. Its non-marine ostracod fauna was previously unknown, although potentially of (palaeo-) zoogeographical interest considering its position. Preliminary surveys of freshwater and brackish habitats on the island in August/September and November/December 2019, revealed a total of 31 species in five families and three superfamilies. Two species are described as new. Vestalenula gravata sp. nov. is a small representative of the family Darwinulidae, characterized by a very long keel on the right valve and the absence of a pigmented eye. This species was found in very shallow streams with poorly sorted substrates in forests. Microloxoconcha semicircularis sp. nov., an interstitial Cytheroidea, was recovered from the tidal part of a small river, the first time this genus has been found in this type of habitat. Two other undescribed species are figured, but left in open nomenclature due to insufficient number of individuals: Vestalenula sp. and Cobanocythere sp. The antennule and antenna of Vestalenula sp. are most similar to those of three species from Brazil.

Symbiotic copepods (Cyclopoida and Siphonostomatoida) collected by light trap from Korea.

Thirty-nine species of symbiotic copepods, comprising 24 species of poecilostome Cyclopoida and 15 species of Siphonostomatoida, are reported from Korean waters, which were collected using underwater light traps at 33 collection sites around the South Korean coast. Ten new species are described: Hemicyclopsrapax sp. nov. in the family Clausidiidae; Pontoclausiacochleata sp. nov. and P.pristina sp. nov. in the family Clausiidae; Heteranthessiusunisetatus sp. nov. in the family Lichomolgidae; Pusanomyicolasensitivus gen. nov., sp. nov. in the family Myicolidae; Polyankylisbogilensis sp. nov. in the family Polyankyliidae; Pseudanthessiuslinguifer sp. nov. in the Pseudanthessiidae; Eupolymniphilusfoliatus sp. nov. in the family Sabelliphilidae; and Acontiophorusestivalis sp. nov. and Thermocherespacificus sp. nov. in the family Asterocheridae. Supplementary descriptions or notes for other species are provided as appropriate.

First record of the genus Boholina (Copepoda, Calanoida, Pseudocyclopidae) in Vietnam, with description of a new species from an anchialine cave in Tra Ban Island.

A new species, Boholina reducta sp. nov., was found in a brackish pool within an anchialine cave in Tra Ban Island in Bai Tu Long Bay, north Vietnam. The new species is clearly distinguished from all the six species currently known in the genus Boholina by the following unique characteristics: reduction of the septum between gonopores; narrow and pointed rostrum; basal segment of mandibular palp armed with three setae; maxillule without seta on the basal exite, and exopod with 11 setae; second and third endopodal segments of the maxilliped bearing three setae each; exopod of male right leg 5 2-segmented, with two strong and one vestigial spines on the outer margin of the distal segment; and last exopodal segment of female leg 5 bearing only one spine on the outer margin. We provide a description of the new species, along with detailed illustrations and scanning electron microscopy photographs. The identification key to Boholina species is updated as well. This is the first record of the genus Boholina from Vietnam.

Taxonomic assessments of some Cyprinotinae Bronstein, 1947 species (Crustacea: Ostracoda) from Japanese and Korean rice fields, including (re-) descriptions of six species and a review of the type species of the subfamily.

Rice is the staple food crop for approximately half the world's population, but some common and abundant taxa inhabiting rice fields, such as ostracods, are poorly studied. For many ostracod species only brief, initial descriptions are available, hindering reliable identifications, and so their ecological roles in rice fields remain obscure. This study partially addresses this problem by assessing the taxonomic validity of six species of Cyprinotinae ostracods reported from rice fields in Japan and South Korea: Cyprinotus  uenoi Brehm, 1936, Hemicypris megalops Sars, 1903, Hemicypris ovata Sars, 1903, Hemicypris vulgaris Okubo, 1990, Heterocypris rotundata (Bronstein, 1928), and Hemicypris kawagaensis Okubo, 2004 nomen nudum. Type material of C. uenoi was not designated and Brehm's ostracod collection is missing, but Japanese and Korean records of C. uenoi differ significantly from Brehm's original description. The Japanese and Korean species is described and named herein as Cyprinotus cassidula sp. nov. Japanese specimens reported to be Hemicypris megalops are probably misidentified, but details of the carapace of Hemicypris megalops are obscure due to poor preservation of type material. Examination of topotype material of Hemicypris posterotruncata Bate, 1970, a sub-fossil from near Lake Turkana in Kenya, demonstrates that this species is extant in Asian rice fields. Investigation of type material of Hemicypris kliei (Lindroth, 1953) has revealed that it is not a senior synonym of Hemicypris posterotruncata, contrary to previous studies. Size and morphological data indicates that Hemicypris vulgaris is a large form of Hemicypris posterotruncata and the two species are treated as synonyms herein. Examination of paralectotypes of Hemicypris ovata indicates that it is very similar to Hemicypris posterotruncata, especially the larger morphotypes, but as these two species can be distinguished by morphological features they are both retained as separate species. However, Japanese records of Hemicypris ovata are considered misidentifications of the larger forms of Hemicypris posterotruncata. Hemicypris kawagaensis, which has only been reported once from East Asia, is herein regarded as a junior synonym of Hemicypris barbadensis Broodbakker, 1983, and is likely an alien species in Asia. Asian specimens previously identified as Heterocypris rotundata show sufficient differences to European specimens to determine that they are not conspecific. This species is described as Heterocypris savatenalintonae sp. nov. Taxonomic descriptions of Hemicypris ovata, Hemicypris posterotruncata, Hemicypris megalops, Hemicypris kliei, Heterocypris savatenalintonae sp. nov., and Cyprinotus cassidula sp. nov. are presented. Finally, it is noted that past redescriptions of Cyprinotus cingalensis Brady, 1886, the type species of the genus and the subfamily Cyprinotinae Bronstein 1947, are based partly on other species.

Ilyocypris (Crustacea: Ostracoda) species in North East Asian rice fields; description of one new species, and redescriptions of Ilyocypris dentifera Sars, 1903 and Ilyocypris japonica Okubo, 1990.

Ilyocypris species are abundant and widespread in North East Asian rice fields, but for many species their taxonomy is poorly defined, which negatively impacts ecological studies on rice field ecosystems. Herein, two of these species, Ilyocypris dentifera Sars, 1903 and Ilyocypris japonica Okubo, 1990, are redescribed, and a third species, Ilyocypris incus sp. nov., is described and named. This latter species has previously been reported from Japan and possibly Korea under the names Ilyocypris angulata Sars, 1903 and I. dentifera, but study of the hemipenes demonstrates that it is a separate species. Ilyocypris nipponica Okubo, 2004 nomen nudum previously reported from Japan is herein considered to be a junior synonym of I. dentifera. Tuberculated and non-tuberculated forms of both I. dentifera and I. japonica were recovered during this study and the presence or absence of tubercles is postulated to be related to environmental conditions, such as water chemistry or predation pressures. Although tuberculated forms of I. dentifera do occur, we concur with some previous studies that Ilyocypris angulata Sars, 1903 should be treated as a separate species, based on features of the hemipenes and carapaces. Figures of the carapaces and hemipenes of I. angulata, and Ilyocypris mongolica Martens, 1991, which is morphologically very close to I. japonica, are also presented for comparisons. This study confirms that three species of Ilyocypris inhabit North East Asian rice fields: I. dentifera, I. japonica and Ilyocypris incus sp. nov. Extant Ilyocypris species in North East Asia, including those from habitats other than rice fields, can be divided into two groups based on the Zenker organ, hemipenis, and sixth limb morphologies. These groups are postulated to represent two distinct lineages of Ilyocypris in North East Asia.

Description of Barathricolathermophilus, a new species from a deep-sea hydrothermal vent field in the Indian Ocean with redescription of the Barathricola type species (Crustacea, Copepoda, Cyclopoida).

Re-study of the type species of the genus Barathricola Humes, 1999 (Copepoda, Cyclopoida, Schminkepinellidae) described from the Pacific Ocean (Juan de Fuca Ridge), and study of the species Barathricolathermophilus sp. nov. from a deep-sea hydrothermal vent field on the Central Ridge in the Indian Ocean revealed a derived feature and widespread geographic distribution of this deep-sea genus of cyclopoids. The derived feature of Barathricola is the sexually dimorphic third endopodal segment of leg 3 possessing a small outer terminal spine together with spine-like outgrowths on this segment. The new species differs from Barathricolarimensis Humes, 1999 in not expressing sexual dimorphism in leg 5, having three spines and one seta on its exopod in both sexes (B.rimensis has three spines and one seta on the female exopod but three spines and two setae on the male exopod) and in having broader caudal rami which are 8.9 times longer than wide in the female (this ratio for B.rimensis is 11). An amended diagnosis of the genus Barathricola, a key and a table of morphological differences for all species of Schminkepinellidae are given.

A new species of Cavernocypris Hartmann, 1964 (Crustacea: Ostracoda) from caves in South Korea.

Surveys of caves in South Korea yielded a new species of the ostracod genus Cavernocypris Hartmann, 1964, herein described as Cavernocypris danielopoli Smith & Kamiya n. sp. This is the fifth described species in this widely distributed genus, and can be discriminated from its congeners by the highly triangular shape of the carapace in lateral view, caused by a large dorsal protrusion on the left valve. A second triangular-shaped morphotype was also collected, differing from the first by a lower carapace and less pronounced dorsal protrusion. As it is not clear at present if this represents a separate species or intraspecific variation, it is left in open nomenclature. The lack of a pigmented eye, a highly triangular carapace and no carapace pigmentation suggests that Cavernocypris danielopoli Smith & Kamiya n. sp. is the most adapted species in the genus to a stygobiotic lifestyle. Another Korean species, Cavernocypris coreana (McKenzie, 1972), found in caves and spring discharges, has a reduced number of antennule segments, common for stygobiotic species, but this feature is lacking in the new species. This suggests that within the genus, species have followed different evolutionary pathways to adapt to the subterranean realm.

A new species of Monstrilla Dana, 1849 (Copepoda: Monstrilloida: Monstrillidae) from Korea, including a key to species from the north-west Pacific.

A new species of monstrilloid copepod belonging to the genus Monstrilla Dana, 1849 is recorded from South Korea. Specimens were obtained between May of 2012 and January of 2014 from inshore waters along the coasts of the East Sea, South Sea, and Jeju Island, using a light trap installed at quays and wharves overnight. Monstrilla ilhoii sp. nov. is characterized by a remarkable combination of a large body size (females about 3.8 mm long, males about 2.8 mm long), a polygonal ridge pattern (cuticular reticulation) over the entire body surface, and an antennule armature featuring a supernumerary spiniform seta (4d3) in females and a dagger-shaped distal spine (62) in both sexes. In other respects M. ilhoii sp. nov. most closely resembles M. lata Desai & Bal, 1963; both species have one and three setae on the endopodal and exopodal lobes, respectively, of female leg 5, a horseshoe-shaped male genital apparatus with marked undulations along the whole distal margin, and six setae on each caudal ramus in both sexes. This paper provides a description of the new species, taxonomic remarks on its morphological features, and differential diagnoses with respect to its allies. Scanning electron microscopy was used to document significant morphological microcharacters. The species of Monstrilla known from five sub-regions of the north-west Pacific are enumerated with the source references, and keys to the females and males of these species are provided.

Two new species of the genus Monstrillopsis Sars, 1921 (Copepoda: Monstrilloida: Monstrillidae) from South Korea.

Monstrilloid copepods of the genus Monstrillopsis Sars, 1921 are recorded from Korea, as well as from the northwestern Pacific, for the first time. Specimens were obtained using a light trap set overnight at piers or seawalls in small harbors. Males of two new species were found and are described herein with remarks on their affinities and detailed drawings and SEM photographs of their morphological features. Monstrillopsis longilobata sp. nov. is allied to M. chathamensis Suárez-Morales & Morales-Ramírez, 2009 and M. sarsi Isaac, 1974 in having the character combination of a long, claw-like apical spinous process on the male antennule and elongate genital lappets. It differs from them in having conspicuous transverse striations on the dorsal surface of the cephalothorax and extremely long male genital lappets, which extend far beyond the anterior margins of the caudal rami. Monstrillopsis coreensis sp. nov. also has a claw-like apical spinous process of the male antennule and conspicuous transverse striations on the dorsal surface of the cephalothorax, but it differs from M. longilobata in having a much longer and stronger apical spine of the antennule and a relatively shorter and undulating genital apparatus.

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.

A new marine cyclopoid copepod of the genus Neocyclops (Cyclopidae, Halicyclopinae) from Korea.

A new cyclopoid species of the genus Neocyclops Gurney, 1927 is described. Type specimens were collected from a beach on south-western coast of the Korean Peninsula by rinsing intertidal coarse sandy sediments. Neocyclops hoonsooi sp. n. is most characteristic in showing the conspicuous chitinized transverse ridges originating from the medial margins of the coxae of all swimming legs. The new species is most similar to Neocyclops vicinus, described from the Brazilian coast, and Neocyclops petkovskii, from Australia. All three species share a large body size (more than 750 µm long), the presence of an exopodal seta on the antenna, two setae on the mandibular palp, the same seta/spine armature on the third endopodal segment of leg 3 (3 setae + 3 spines), and the fairly long inner distal spine on the third endopodal segment of the female leg 4. However, Neocyclops hoonsooi sp. n. differs from both species by the much shorter caudal rami (less than 1.7 times as long as wide) and the shorter dorsal caudal seta VII. Furthermore, Neocyclops hoonsooi is clearly distinguished from Neocyclops vicinus by the 10-segmented antennule (vs 12 segments in Neocyclops vicinus), and from Neocyclops petkovskii by the elongate inner distal spine on leg 5 exopod and the 3-segmented leg 5 in male (vs 4-segmented in Neocyclops petkovskii). A tabular comparison of characters separating Neocyclops hoonsooi from its closest allies and a key to Neocyclops species from the Indo-Pacific Ocean are provided. This is the first record of the genus Neocyclops from the northern Pacific.

Zelinkaderes yong sp. nov. from Korea - the first recording of Zelinkaderes (Kinorhyncha: Cyclorhagida) in Asia.

BACKGROUND: A new kinorhynch species, Zelinkaderes yong sp. nov., is described from Korea. RESULTS: Zelinkaderes yong sp. nov. is described from coastal, sandy habitats in Korea by means of light and scanning electron microscopic techniques. The new species is characterized by the presence of cuspidate spines in lateroventral positions on segments 2 and 9, ventrolateral positions on segment 5, and lateral accessory positions on segment 8; flexible tiny acicular spines in lateroventral positions on segment 2, more regular-sized lateroventral acicular spines on segment 8, and middorsal spines on segments 4, 6, 8, 9, and 11. Females furthermore have acicular spines in middorsal and midlateral positions on segment 10, whereas males have crenulated spines on this segment. The absence of acicular spines in the lateral series of segment 9 makes it easy to distinguish the new species from all previously described congeners. The new species differs most from Zelinkaderessubmersus,whereas it is morphologically closest to Zelinkaderesklepali.In regard to the spine patterns, the new species only differs from Z. klepali by its lack of lateroventral acicular spines on segment 9. CONCLUSIONS: The finding of a new species of Zelinkaderes in East Asia extends the distributional range of the genus, which suggests that the genus basically could be present anywhere in the world and could be considered as cosmopolitan.

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.

Description of three new Tetranchyroderma gastrotrichs (Macrodasyida: Thaumastodermatidae) from South Korea.

The present paper deals with description of three new marine gastrotrich species belonging to the genus Tetranchyroderma with a new record for Korea of T schizocirratum Chang, Kubota & Shirayama, 2002, on the basis of specimens from the Korean coast. Tetranchyroderma anisoankyrum sp. nov. is differentiated from congeners by its dorsal cuticular armature of pentancres with central tine longer than the others, a pair of rod-like cephalic tentacles, 2 cirratum-type TbDL, 13-14 cirratum-type TbL per side, and a pair of TbL. Tetranchyroderma coreense sp. nov. is distinguished from other pentancrous species by cirratum-type tubes of 2 TbDL, one TbL, 3-4 TbVL, paired foot-type TbV, and absence of cephalic tentacles. Tetranchyroderma oblongum sp. nov. is characterized by the character combination of cuticular armature of tetrancres, 7 dorsolateral and 7-9 lateral cirratum-type tubes, and 33-38 TbVL along whole body. This brings the total number of species in the genus Tetranchyroderma known from South Korea to 12.

Monophyly of the family Desmoscolecidae (Nematoda, Demoscolecida) and its phylogenetic position inferred from 18S rDNA sequences.

To infer the monophyletic origin and phylogenetic relationships of the order Desmoscolecida, a unique and puzzling group of mainly free-living marine nematodes, we newly determined nearly complete 18S rDNA sequences for six marine desmoscolecid nematodes belonging to four genera (Desmoscolex, Greeffiella, Tricoma and Paratricoma). Based on the present data and those of 72 nematode species previously reported, the first molecular phylogenetic analysis focusing on Desmoscolecida was done by using neighbor joining (NJ), maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI) methods. All four resultant trees consistently and strongly supported that the family Desmoscolecidae forms a monophyletic group with very high node confidence values. The monophyletic clade of desmocolecid nematodes was placed as a sister group of the clade including some members of Monhysterida and Araeolaimida, Cyartonema elegans (Cyartonematidae) and Terschellingia longicaudata (Linhomoeidae) in all the analyses. However, the present phylogenetic trees do not show any direct attraction between the families Desmoscolecidae and Cyartonematidae. Within the monophyletic clade of the family Desmoscolecidae in all of the present phylogenetic trees, there were consistently observed two distinct sub-groups which correspond to the subfamilies Desmoscolecinae [Greeffiella sp. + Desmoscolex sp.] and Tricominae [Paratricoma sp. + Tricoma sp].

Pseudobiotus spinifer, a new tardigrade species (Eutardigrada: Hypsibiidae) from Nakdong River, South Korea, with a redescription of P. vladimiri Biserov, Dudichev & Biserova.

A new freshwater tardigrade species, Pseudobiotus spinifer sp. nov., is described from the sand bottom of Nakdong River, South Korea. The new species is most similar to Pseudobiotus vladimiri from Biwa Lake, Japan, but differs from it by having small accessory points ending in the center of the primary branches of all claws, relatively longer claws and macroplacoids, and well developed cuticular spines/spicules over most of the dorsal and lateral surfaces of the body. Pseudobiotus vladimiri is redescribed on the basis of the holotype. A revised key to the species of the genus Pseudobiotus is also given.

Partial mitochondrial gene arrangements support a close relationship between Tardigrada and Arthropoda.

Regions (about 3.7-3.8 kb) of the mitochondrial genomes (rrnL-cox1) of two tardigrades, a heterotardigrade, Batillipes pennaki, and a eutardigrade, Pseudobiotus spinifer, were sequenced and characterized. The gene order in Batillipes was rrnL-V-rrnS-Q-I-M-nad2-W-C-Y-cox1, and in Pseudobiotus it was rrnL-V-rrnS-Q-M-nad2-W-C-Y-cox1. With the exception of the trnI gene, the two tardigrade regions have the same gene content and order. Their gene orders are strikingly similar to that of the chelicerate Limulus polyphemus (rrnL-V-rrnS-CR-I-Q-M-nad2-W-C-Y-cox1), which is considered to be ancestral for arthropods. Although the tardigrades do not have a distinct control region (CR) within this segment, the trnI gene in Pseudobiotus is located between rrnL-trnL1 and trnL2-nad1, and the trnI gene in Batillipes is located between trnQ and trnM. In addition, the 106-bp region between trnQ and trnM in Batillipes not only contains two plausible trnI genes with opposite orientations, but also exhibits some CR-like characteristics. The mitochondrial gene arrangements of 183 other protostomes were compared. 60 (52.2%) of the 115 arthropods examined have the M-nad2-W-C-Y-cox1 arrangement, and 88 (76.5%) the M-nad2-W arrangement, as found in the tardigrades. In contrast, no such arrangement was seen in the 70 non-arthropod protostomes studied. These are the first non-sequence molecular data that support the close relationship of tardigrades and arthropods.

A new culture system for in situ observation of the growth and development of Eucyclops serrulatus (Copepoda: Cyclopoida).

A practical and convenient method of rearing Eucyclops serrulatus in a microculture environment is described. A complete life cycle of E. serrulatus was maintained in a narrow space on a microscope slide glass on which a cover glass of 22 x 40 mm in size was mounted at a height of 0.8 mm. The culture medium was constituted by bottled mineral water boiled with grains of Glycine max (soybean). Chilomonas paramecium, a free-living protozoan organism, was provided as live food. Growth of nauplii hatched from eggs to the first stage of copepodite took an average of 7.7 days, and the growth of copepodite 1 to the egg-bearing adult female took an average of 20.1 days in the microculture cell with an average life time of 44.7 days. Continuous passage of copepods was successfully maintained as long as sufficient medium and food were provided. The microculture method enables an in situ microscopic observation on the growth and developmental process of helminth larvae experimentally infected to copepods as well as of copepod itself. Furthermore, it does not require anesthetization and, therefore, minimize the amount of stress exposed to copepods during the handling process.

Two new marine gastrotrichs of the genus Ptychostomella (Macrodasyida, Thaumastodermatidae) from South Korea.

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.

A new species of parastenhelia (Copepoda: Harpacticoida: Parastenheliidae) from Korea.

A new species belonging to the genus Parastenhelia of family Parastenheliidae is described on the basis of the specimens of both sexes collected from the zosteran bed at Seungbong Island and from the shallow sandy bottoms of Jeju Island in Korea. It is distinguished from the congeners by its character combination of inserted location and the length proportion of the inner seta on the first endopodal segment of leg 1, shape of female leg 5, the modified male legs 2-3 endopods, and the number of setae on male leg 5 exopod. An emended table of morphological characters for the genus is provided.