The subgenus Tricoma Cobb, 1894 comprises free-living marine nematodes encompassing a total of 83 validated taxa. Within this diversity, twenty-one taxa thrive in the deep sea, while twenty-three are found in coral reefs, flat areas, or green algae. Additionally, eleven taxa inhabit the sublittoral zone at depths exceeding 10 meters, and the remaining taxa are situated on beaches, coasts, or in habitats lacking detailed information. In the course of a survey focused on the East Sea free-living marine nematodes, we identified four new and two previously unrecorded species belonging to the subgenus Tricoma. Specifically, two new species, Tricoma (Tricoma) breviseta sp. nov. and T. (T.) donghaensis sp. nov., were discovered in mud-sandy sediment in deepsea environments below 2000 meters within the Ulleung Basin and Hupo Bank. Two previously unrecorded species [T. (T.) paralucida Decraemer, 1987 and T. (T.) similis Cobb, 1912] and the two newly found species [T. (T.) longicauda sp. nov. and T. (T.) ulleungensis sp. nov.] were obtained from subtidal coarse sand at a depth of 20 meters during a survey of the waters surrounding Ulleungdo Island. The distribution and information on validated taxa within the subgenus Tricoma were systematically collected, reviewed, and cataloged. Detailed morphological features and illustrations of Tricoma species from Korea were provided through the use of differential interference contrast microscopy.

Three free-living marine nematodes (Desmoscolex (Desmoscolex) max Timm, 1970, Daptonema longiapophysis Huang and Zhang, 2010, and Pseudosteineria sinica Huang and Li, 2010) were newly recorded in Korea. Desmoscolex (D.) max was found from subtidal coarse sediment around Wangdolcho in the East Sea. It was characterized by the presence of untypical setae arrangement, obviously elongated triangle-shaped head, long hairy cephalic setae, a long naked tail spinneret, and the absence of peduncle at the base of somatic setae. Daptonema longiapophysis was obtained from intertidal sandy sediments in the southern coast of Korea. It was characterized by the presence of setiform labial sensilla, spicules with a projection on both sides, and gubernaculum with dorso-caudal apophysis. Pseudosteineria sinica was discovered from the intertidal sediment in the Yellow Sea. It was characterized by unobservable amphideal fovea, different lengths of spicules, and gubernaculum with dorso-caudal apophysis. In this study, we provide detailed morphological features of three free-living marine nematodes by differential interference contrast microscopy.

During a survey of free-living marine nematodes of Korea, two new marine desmoscolecid nematodes belonging to subgenus Quadricoma Filipjev, 1922 were discovered. Tricoma (Q.) jejuensis sp. nov. and T. (Q.) unipapillata sp. nov. are described based on specimens obtained from washings of coarse sediments from eastern and southern coasts of Korea. Tricoma (Q.) jejuensis sp. nov. is characterized by having 33 quadricomoid body rings and inversion at main ring 23, pentagonal head with truncated anterior end, a pair of ocelli situated at main ring 6, somatic setae comprising of 8 pairs of subdorsal setae and 12 pairs of subventral setae, and relatively short spicules (42-46 μm long). Tricoma (Q.) unipapillata sp. nov. is characterized by 44 quadricomoid body rings and inversion at main ring 32, somatic setae comprising of 7 pairs of subdorsal setae and 10 pairs of subventral setae, globular head truncated anterior end, relatively short and stumpy cephalic setae with cuticular flange, one single naked ventral median genital papillae situated on main ring 20, and spicules with a proximally marked capitulum. Detailed morphological descriptions and illustrations of these two new species are provided in this study.

A new free-living marine nematode species of the genus Pseudosteineria Wieser, 1956 affiliated with the family Xyalidae is described based on specimens collected from the sediment of a subtidal benthic environmental habitat in the East Sea, Korea. Pseudosteineria varisetis sp. nov differed from its congeners by the combination of the following characteristics: a relatively long body (1,628-1,691 μm long in males), a circular amphideal fovea situated behind the subcephalic setae, the presence of lateral cuticular alae starting from behind the nerve ring, the presence of eight groups of long subcephalic setae, the presence of irregularly distributed variable lengths of somatic setae on the body, solid spicules (43.2-43.9 μm long) with a cephalated proximal end, a long tubular shaped gubernaculum with dorsal swelling, and a conico-cylindrical tail with two to four terminal setae. In this report, we provide a taxonomic description and illustrations of a new species of the genus Pseudosteineria by differential interference contrast microscopy.

Admirandus multicavus Belogurov and Belogurova, 1979, a new record of free-living marine nematode species belonging to family Oncholaimidae is reported based on the specimens collected from the intertidal sediments of Korea. Admirandus multicavus is characterized by the following unique characteristics: cephalic setae (1-2 μm long), spicules (71-126 μm long) and gubernaculum (15-31 μm long), midventral preanal supplementary organ, three glandular duct openings of the Demanian system, and stoma length measuring twice the width. A comparative analysis of the biogeographical and ecological characteristics of Admirandus species is presented. DIC (Differential interference contrast) photomicrographs of the species are also provided herein. This report represents the first taxonomic analysis of the genus Admirandus Belogurov and Belogurova, 1979 discovered from the Korean seawaters.

Two new free-living marine nematodes of the genus Belbolla Andrássy, 1973 belonging to family Enchelidiidae are newly described based on specimens obtained from a shallow subtidal sediment of the western and southern outermost islands of Korea. Belbolla koreensis sp. nov. differs from other species of the genus by the combination of the following characteristics: longer body length (3,080-3,462 μm long), eight oesophageal bulbs in the posterior region of pharynx, well-developed two winged precloacal supplements (anterior precloacal supplement slightly longer than posterior one: 47-59 μm vs. 43-46 μm long), strongly arcuated, very thick, L - shaped spicule (122- 127 μm long, 1.7-1.9 anal body diameter (a.b.d.) long) with three separated blunt distal tips, and well-developed relatively long cylindrical shaped gubernacular apophysis with blunt teeth covering two thirds of the dorsal margin (57-58 μm long, 0.8-0.9 a.b.d. long). Belbolla hoonsooi sp. nov. is characterized by the following combination of characteristics: longer body length (3,494 μm long), eight oesophageal bulbs in the posterior region of pharynx, well-developed two winged precloacal supplements (anterior precloacal supplement slightly longer than posterior one: 43 μm vs. 36 μm long), strongly arcuated, L - shaped spicule (119 μm long, 1.5 a.b.d. long) with three separated blunt distal tip, and well-developed relatively long inverted triangle shaped gubernacular apophysis with blunt teeth covering half of the dorsal margin (45 μm long, 0.6 a.b.d. long). Detailed morphological characteristics and illustrations of two new Belbolla nematodes from the Korean seawaters were provided by differential interference contrast microscopy. Comparative tables on biogeographical and morphological characteristics of Belbolla species are also provided herein.

A new free-living marine nematode species of the genus Belbolla Andrássy, 1973 belonging to the family Enchelidiidae is described based on specimens collected from the sediment of a subtidal benthic environmental habitat in the East Sea, Korea. Belbolla wonkimi sp. nov. differs from its congeners by the combination of the following characteristics: a relatively long body (3263-3396 μm), the absence of ocelli, nine oesophageal bulbs in the posterior pharynx, well-developed two winged precloacal supplements, longer spicule length (115-130 μm, 1.6-1.8 anal body diameter long), and a triangle-shaped shorter gubernacular apophysis (17-18 μm). Comparative tables on the biogeographical and morphological characteristics of Belbolla species are presented. A DIC (differential interference contrast) photomicrograph of the new species is also provided. This is the first taxonomic report on the genus Belbolla from Korean waters.

본 연구는 가막만에 서식하는 중형저서동물의 계절적인 변화와 공간분포 특성을 연구하였다. 2009~2010년에 걸쳐 10개 정점에서 2월, 6월 10월에 총 6회 조사를 실시하였다. 가막만에 서식하는 중형저서동물의 군집구조, 분류군 다양 도, N/C ratio를 분석하였다. 연구기간 동안 선형동물과 저서 성 요각류의 서식밀도가 가막만의 중형저서동물 그룹중 가 장 높은 서식밀도를 나타냈다. 분류군 다양도 값은 가막만의 내만역에 비해 외해에 인접한 정점들이 높은 값을 나타냈다. N/C ratio는 각 지역별로 저서생태계의 오염을 모니터링 하 기 위한 지수인데, N/C ratio 분석결과 가막만의 내만역의 N/ C ratio 값이 외해에 인접한 정점들에 비해 높은 값을 나타내 내만역의 오염도가 상대적으로 높은 값을 나타냈다.