Eight samples, collected from six moss-covered soil and two freshwater samples, were examined to determine ciliate diversity in Korea. Based on the morphology of living and stained specimens, thirteen ciliate species, previously unrecorded in Korea, were identified. These specimens were classified to four classes, seven orders, ten families, and twelve genera. Of these genera, the following six were first records in Korea: Bresslauides, Dexiotricha, Glaucoma, Paragastrostyla, Sathrophilus, and Trithigmostoma. Here, we provide a brief description of the morphology of these 13 taxa along with microphotographs and notes.

Taeniacanthid copepods Anchistrotos kojimensis Do and Ho, 1983 were collected from the branchial cavities of stichaeid fish, Ernogrammus hexagrammus (Schlegel) and yellowfin goby, Acanthogobius flavimanus (Temminck and Schlegel) in Korean waters. Here, we provide the first description of a male of Anchistrotos Do and Ho, 1983. A close comparison of the specimens of A. kojimensis collected from Korea with the original description revealed differences in the adult female: (1) the caudal ramus bears seven setae (seta I minute); (2) the maxillule with small knob-like process anteriorly; (3) leg 5 ornamented with patched spinules distally and having row of spinules at base of each spine and distal seta. The first description of the adult male reveals the following features: (1) the distal abdominal somite had rows of spinules anteriorly and near insertion of each caudal ramus; (2) the postantennal process is more elongate than in the female; (3) the basis of maxilliped is with two prosimomedial setae, two longitudinal rows of stout denticles found on posteromedial surface and row of spinules on anteromedial surface; and (4) the second endopodal segment is a strongly curved claw, with a row of stout denticles along a concave margin, two long and one small setae.

Twelve ciliates were collected from freshwater, marine, and brackish water habitats in Korea and taxonomic descriptions are provided based on observations of living cells and protargol-impregnated specimens. These ciliates, recorded for the first time in Korea, were classified into 12 genera, 11 families, 10 orders, and five classes. We provide brief descriptions and remarks, including microphotographs, for the 12 ciliates: Allotricha mollis, Amphileptus eigneri, Didinium gargantua, Holophrya teres, Lacrymaria marina, Novistrombidium apsheronicum, Pelagostrobilidium conicum, Pseudochilodonopsis fluviatilis, Pseudourostyla subtropica, Strombidium conicum, Urocentrum turbo, and Uronema marinum.

Rotifers collected from various terrestrial and aquatic habitats such as mosses on trees or rocks, tree barks, wet mosses and wet leaf litter at streams, and dry leaf litter at four different locations in Korea, were investigated. Thirteen species belonging to nine genera in five families of monogonont and bdelloid rotifers were identified: Bryceella perpusilla Wilts, Martinez Arbizu and Ahlrichs, 2010, Collotheca ornata (Ehrenberg, 1830), Habrotrocha flava Bryce, 1915, H. pusilla (Bryce, 1893), Macrotrachela aculeata Milne, 1886, M. plicata (Bryce, 1892), Mniobia montium Murray, 1911, M. tentans Donner, 1949, Notommata cyrtopus Gosse, 1886, Philodina lepta Wulfert, 1951, P. tranquilla Wulfert, 1942, Pleuretra hystrix $Barto{\check{s}}$, 1950 and Proalinopsis caudatus (Collins, 1873). All these rotifers are new to Korea, and B. perpusilla, H. flava, M. montium, P. caudatus, P. hystrix and P. lepta are new to Asia as well. Of interest, the present study is the first to record B. perpusilla outside its type locality. In addition, P. lepta has previously been recorded from only three European countries.

This study describes a new species of cytheroid ostracod, Paradoxostoma koreana sp. nov., collected in Korea. In addition, three other cytheroid ostracods, P. setoense Schornikov, 1975, Loxoconcha pulchra Ishizaki, 1968, and Ishizakiella miurensis (Hanai, 1957), are reported with brief descriptions and images. Paradoxostoma setoense and L. pulchra were previously only known from Japan, while I. miurensis was previously reported from Korea. Here, we describe variability in hemipenis morphology observed in the Korean population. The new species is closely related to several East Asian species, but its sister species is P. rhomboideum Okubo, 1977. The primary difference between the new species and P. rhomboideum is morphology of the distal projections of the hemipenis, but minor differences exist in the details of the cheatotaxy of other appendages. This report also provides a list of all East Asian Paradoxostomatidae.

There are five known species of the genus Tmarus (Thomisidae) in Korea to date: Tmarus horvathi Kulczyn'ski, 1895, Tmarus koreanus Paik, 1973, Tmarus orientalis Schenkel, 1963, Tmarus piger (Walckenaer, 1802) and Tmarus rimosus Paik, 1973. Two females of Tmarus yaginumai Ono, 1977, which was previously only known in Japan, were collected by sweep net between the shrubs at hillocks near the coast of Korea and are described with taxonomic illustrations.

A pagurid crab, Pagurus erythrogrammus is described and illustrated for the first time from Korean waters. It was collected by SCUBA diving in Seogwipo (Jejudo Island) on 30 May 2013. Its morphology is similar to those of known Korean species of the family Paguridae: Boninpagurus pilosipes, Pagurus nigrivittatus, and Pagurus quinquelineatus. This species, however, it is distinguished by having a developed rostrum, seven rows of spines on dorsal surface of the right palm in male, a row of spines on the medial surface of the dactylus of the third pereopod, 12 long ventral spines of dactylus of the third pereopod, six small spines on the concaved distal margin of telson, and three reddish brown lines on lateral surfaces of propodi of the second and third pereopods.

During a study of acarine biodiversity, a phytoseiid mite was collected from soil samples under the rose of Sharon plants. The specimen was identified as Neoseiulus harrowi Collyer, 1964, which was previously only reported in New Zealand and Australia, and is thus a new record for Korean phytoseiid fauna. Neoseiulus harrowi is morphologically similar to N. makuwa (Ehara), but distinctly different in two characters: shorter length of two posterior setae (Z4, Z5) and a forked atrium of spermatheca longer in N. makuwa than in N. harrowi in females.

Three ciliate species, Frontonia schaefferi Bullington, 1939, Spathidium curiosum Foissner, 2016, and S. muscicola Kahl, 1930, were collected from freshwater and terrestrial habitats in Korea. Their morphology was investigated based on live observations and protargol impregnation. Frontonia schaefferi was characterized by a cell size of $89-112{\times}45-53{\mu}m$ (after protargol impregnation) and three vestibular kineties. Spathidium curiosum was characterized by a cell size of ca. $125{\times}25{\mu}m$ in vivo and the unusual shape of the extrusomes. Spathidium muscicola was characterized by a cell size of ca. $135{\times}40{\mu}m$ in vivo and four to six macronuclear nodules. These three species are new records for Korea.

Three ciliate species, Australocirrus australis (Foissner, 1995) Kumar and Foissner, 2015, Rimaleptus longitrichus ($Vd^{\prime}a{\check{c}}n{\acute{y}}$ and Foissner, 2008) $Vd^{\prime}a{\check{c}}n{\acute{y}}$ and Foissner, 2012, and Frontonia subtropica Pan et al., 2013, that were previously unreported in Korea were collected from terrestrial and marine habitats in Korea. Using live observation and protargol impregnation, the three species were identified using a combination of the following characteristics: Australocirrus australis, the distance between the anterior pretransverse cirrus and the anteriormost transverse cirrus (0.6-2.1% of body length) and the arrangement of the transverse cirri (oblique row); Rimaleptus longitrichus, the arrange of contractile vacuoles and longitudinal ciliary rows anteriorly spaced; Frontonia subtropica, number of somatic kineties (approximately 115 rows) and vestibular kineties (5 rows).

A specimen of the oribatid mite, Gustavia aominensis Fujikawa, 2008, was isolated from litter and soil samples of Sasa borealis at Cheongok Mountain Natural Recreation Forest in Bonghwa, Gyeongbuk, Korea. This is the first record of this species in Korea. We provide detailed illustrations of the diagnostic features of this species relative to the original description as well as a key for Korean Gustavia species along with illustrations.

As a part of a survey of indigenous biological resources of Korea, 30 marine benthic foraminiferal species belonging to 24 genera and seven orders (Astrorhizida, Lagenida, Lituolida, Miliolida, Robertinida, Rotaliida and Textulariida) were identified. Bottom sediment samples were collected from eight stations on the west and east coast of South Korea, in April 2015 and May 2016, respectively. Ten species belonging to nine genera and five orders (Lagenida, Lituolida, Robertinida, Rotaliida, Textulariida) were identified in the Yellow Sea. Among these taxa, Rotaliida was the dominant order, represented by four species: Evolvocassidulina tenuis (Phleger & Parker, 1951), Cibicides mabahethi Said, 1949, Cibicides pseudolabatulus Perelis & Reiss, 1975 and Cibicidoides barnetti Bermudez, 1949. Twenty species belonging to 15 genera and five orders (Astrorhizida, Lagenida, Lituolida, Miliolida, and Rotaliida) were identified from the East Sea and the Lagenida was the dominant order, represented by 11 species: Lagena strumosa Reuss, 1858, Lagena nebulosa (Cushman, 1923), Lagena striata var. semiornata Reuss, 1863, Procerolagena cylindrocostata Albani & Yassini, 1989, Fissurina bispinata $Ujii{\acute{e}}$, 1963, Oolina laevigata d'Orbigny, 1839, Polymorphina amplissima McCulloch, 1977, Polymorphina subelliptica McCulloch, 1977, Guttulina succincta McCulloch, 1977, Guttulina neoproblema McCulloch, 1977 and Lagenosolenia obtecta McCulloch, 1977. The findings described here increased the number of foraminiferal species in Korea to approximately 1060, and contribute to our understanding of the diversity of foraminifera in Korean waters.

Eleven new species of two genera, Psammocinia and Ircinia (Demospongiae: Dictyoceratida: Irciniidae) are described from Gageo Island, Ulleung Island and Jeju Island, South Korea. The separation of these two genera was made on basis of morphological evidence, especially skeletal structure with foreign debris. Six new species of Psammocinia and five new species of Ircinia were added to known fauna. All skeletal fibres are very irregular.

We collected three soil ciliates, Colpoda maupasi Enriquez, 1908, Tillina minima Alekperov, 1985, and Gonostomum singhii Kamra et al., 2008, in Korea. The two genera, Colpoda and Tillina, belong to the class Colpodea, and the other, Gonostomum belongs to the class Spirotrichea. We describe these species based on observations of live and protargol-impregnated specimens.

Seven species of the families Cybaeidae and Gnaphosidae are reported. Cybaeus auriculatus n. sp., C. parvus n. sp. and Haplodrassus miryangensis n. sp. are described from Gyeongsang-do, Korea. Drassodes platnicki Song, Zhu and Zhang, 2004, Haplodrassus hatsushibai Kamura, 2007, Zelotes eskovi Zhang and Song, 2001 and Z. xiaoi Yin, Bao and Zhang, 1999 are newly recorded to the spider fauna of Korea.

Three species in the genus Aetea (Bryozoa: Cheilostomata: Aeteidae) are described: Aetea anguina (Linnaeus, 1758), A. ligulata Busk, 1852, and A. truncata (Landsborough, 1852). Aetea ligulata Busk, 1852 and A. truncata (Landsborough, 1852) are new records of Korean bryozoan fauna. Four of the 17 species in the genus Aetea Lamouroux, 1812 are cosmopolitan or widespread. Three of these species (Aetea sica (Couch, 1844) was not observed) are reported in this study.

This study aims to investigate the freshwater bryozoans of Jeju Island off the Korean Peninsula for the first time. To date, twelve species has been reported from the mainland of Korea. However, no study of freshwater bryozoans has ever been conducted on Korean islands including Jeju Island, which is the largest island in Korea. Five species in three genera Fredericella, Plumatella and Stephanella, from Jeju Island are described. Of which, three species, Fredericella indica, Plumatella mukaii and P. rugosa, are new records of Korean bryozoan fauna. As a result of this study, the number of identified Korean freshwater bryozoans is now 15 species, including 12 phylactolaemates and three gymnolaemates.

Seven new species in two genera, Sarcotragus and Bergquistia (Demospongiae: Dictyoceratida: Irciniidae), are described from Jeju Island, Korea. The separation of the two genera was made on basis of morphological evidence in skeletal structure, especially fasciculation of primary fibres and filament thickness. Two new species in the genus Sarcotragus and five new species in the genus Bergquistia are compared with other reported species.

Assocations of wingless mites with winged arthropods highlight important life history strategies and ecological interactions. Here we report a mesostigmatan mite species association with an earth-boring dung beetle. Mite spciemens were collected from the soil of organic apple orchards in the Province of Gyeongsangbuk-do, Republic of Korea, and cattle dung was collected from grassland in Mongolia. The species was identified as Alliphis necrophilus Christie, 1983 (Acari: Eviphididae). This is the first report of any species in the genus Alliphis in Korea. Some descriptive details and ecological remarks are also provided.

Four feather mite species, Grallobia fulicae (Trouessart, 1885), Grallobia gallinulae Gaud, 1968, Grallolichus proctogamus (Trouessart, 1885) and Megniniella gallinulae (Buchholz, 1869), previously unrecorded in South Korea are reported. Specimens of Grallobia fulicae and Grallolichus proctogamus were collected from the eurasian coot, Fulica atra in Cheongju-si. Grallobia gallinulae and M. gallinulae were found on the common moorhen, Gallinula chloropus in Yesan-gun. The genera Grallobia Hull, 1934, Grallolichus Gaud, 1960 and Megniniella Gaud, 1958 are new records for South Korea. Here, we provide illustrations and morphological descriptions of these four feather mite species as well as the partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI) as DNA barcodes.

A research project entitled "Discovery of Korean Indigenous Species" was launched in 2006, and has been carried on as a continuous project until now. The main purpose of this project is to find undiscovered species on the Korean peninsula and ultimately register these species in the "National List of Species of Korea". In this paper, we present 79 unrecorded species of the Korean metazoans. All species were obtained from the final reports of "Discovery of Korean Indigenous Species" which were performed during the first five years of the project, 2006 to 2010.

In this list-format paper, we present unrecorded species of Korean ciliates (phylum Ciliophora). All species were selected from the final reports of the project: "Discovery of Korean Indigenous Species". This project has been carried out to discover and record various Korean indigenous species since 2006 and is funded by the National Institute of Biological Resources (NIBR). Among the various species, ciliates were a major taxon that was highlighted in this project as a speciose group categorized under Protozoa. This paper contains reports of 38 ciliates (8 classes, 16 orders, 23 families, and 34 genera) observed in Korea during the initial five years of the project (2006-2010).

Two feather mites, Scutomegninia phalacrocoracis Dubinin and Dubinina, 1940 and Ptiloxenus major ($M{\acute{e}}gnin$ and Trouessart, 1884) are reported for the first time in Korea. Specimens of S. phalacrocoracis and P. major were collected from the great cormorant, Phalacrocorax carbo and great crested grebe, Podiceps cristatus, respectively. The genera Scutomegninia Dubinin, 1951 and Ptiloxenus Hull, 1934 are also new reports for South Korea. Here, we provide morphological descriptions and illustrations of these two species. Additionally, we provide partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI) as DNA barcodes.

The genus Phyllopodopsyllus T. Scott, 1906 is nearly cosmopolitan and contains around 60 valid species, but has not been previously recorded in Korea. One of the reasons is probably the paucity of research in marginal habitats, such as marine interstitial. I describe two new species here. Numerous specimens of both sexes of P. kitazimai sp. nov. were collected from a beach near Yeongdeok, while only two females of P. busanensis sp. nov. were collected from a beach near Busan. The new species differ in numerous macro-morphological characters, such as the segmentation and armature of the antennula, armature of the mandibula, maxillula, maxilliped, and the first three swimming legs, as well as the shape of the caudal rami and the female genital field. However, they show very little difference in the number and position of cuticular organs (pores and sensilla) on all somites, which might prove these rarely used micro-characters to be useful in the reconstruction of phylogenetic relationships in this group of harpacticoids. Both species have their closest relatives in Japan. Phyllopodopsyllus kitazimai is morphologically most similar to P. punctatus Kitazima, 1981, but can be distinguished by much longer third exopodal segments of the third and fourth swimming legs. Phyllopodopsyllus busanensis shares the largest number of morphological similarities with P. setouchiensis Kitazima, 1981, but can be distinguished by shorter caudal rami. A key to species is also provided.

Two species new for Korea, Scolopocryptops nigrimaculatus Song, Song and Zhu, 2004 and Scolopocryptops mushashiensis Shinohara, 1984 are reported from South Korea. The Korean occurrance of S. nigrimaculatus is the first record of the species outside China, while S. mushashiensis has been known only form its type locality in Japan till now.

We briefly report the observation of five ostracod species: Scottia birigida Smith, Matzke-Karasz, Kamiya and Ikeda, 2002; Codonocera mortenseni Poulsen, 1962; Pyrocypris noctiluca Kajiyama, 1912; Euconchoecia cf. chierchiae Muller, 1890; and E. pacifica Chavtur, 1976. All five species are new records of Korean ostracod fauna. Specimens were collected during the 2014-2016 Korean Indigenous Species project. For three species we also include mtCO1 sequences. Currently, there are 65 published reports of indigenous Korean ostracod species.

A study of the Cladocera (Crustacea: Branchiopoda) from the Korean Peninsula resulted in the checklist of Jeong et al. (2014). Several sampling campaigns conducted by our team since 2014, with the framework of the programs supported by the National Institute of Biological Resources (NIBR), have resulted in a considerable increase in the number of water bodies studied in South Korea. In this report, seven new records for the Korean Peninsula are provided: (1) Macrothrix vietnamensis Silva-Briano, Dieu and Dumont, 1999; (2) Disparalona chappuisi (Brehm, 1931); (3) Pleuroxus(Picripleuroxus) quasidenticulatus (Smirnov, 1996); (4) Acroperus africanus Neretina and Kotov, 2015; (5) Alona ossiani herricki Sinev, 2013; (6) Coronatella trachystriata (Chen, Zhang and Liu, 1994); (7) Leydigia louisi Jenkin, 1934. Most of these taxa belong to the southern thermophilic complex. In addition several populations of Pleuroxus (Picripleuroxus) denticulatus Birge, 1879 and Pseudochydorus globosus (Baird, 1843) were re-studied, and their presence in Korea is confirmed. Through increased collection efforts and the application of molecular methods we are confident that more new records of Korean fauna will be published in the near future.