Species diversity of free-living marine nematodes in Korea with taxonomic and molecular phylogenetic studies of the family Ironidae and Thoracostomopsidae

Abstract

While extensive studies have been conducted worldwide on the free-living marine nematodes, they still remain classified as unexplored taxa in Korea. Compared to approximately 7,000 species of free-living marine nematodes recorded worldwide, a small fraction of that (approximately 50 species) have been recorded in Korea. For this PhD thesis, coastal regions of entire Korean peninsula were surveyed over the span of three years (2015-2017) through a project “National Investigation of Marine Ecosystem”. As a result, 5,222 specimen of free-living marine nematodes were examined and identified to genus and/or species level. Identified nematodes belonging to 2 classes, 8 orders, 37 families, 161 genera and 458 species were recorded from coasts of Korea. Selected four genera belonging to families Ironidae and Thoracostomopsidae were reviewed and revised bibliographically along with description of three new species and two unrecorded species. The descriptions are accompanied with revised diagnosis of the respective genera, compiled tabular key consisting of all significant measurements of all valid congeners and new identification key to the genus. In some cases, pictorial key consisting of retraced illustration of head and tail, mtCOI (JB3/JB5) and 18S rRNA (MN18F/22R) sequences and their reflective molecular phylogenetic analysis are provided. |해양자유생활 선형동물에 대한 광범위한 연구가 수행되었지만 여전히 한국에서는 미개척 분류군이다. 전 세계적으로 약 7,000종의 해양자유생활 선형동물이 기록되었지만, 국내에서 기록된 종 수는 약 50종이다. 3년간의 연구를 통해 국내 해안에 서식하는 선형동물을 파악하였고, 총 8목 37과 161속 458종이 서식하는 것을 확인했다. 또한 Ironidae 및 Thoracostomopsidae과에 속하는 4개의 속 (Thalassironus De Man, 1889; Mesacanthion Filipjev, 1927; Enoplolaimus de Man, 1893; Enoploides Ssaveljev, 1912)에 대한 재검토를 진행 및 신종 3종과 미기록종 2종을 본 연구를 통해 기재하였다. 일부 종의 mtCOI (JB3/JB5) 및 18S rRNA (MN18F/22R)를 사용하여 분자계통학적 분석을 진행하였다.; While extensive studies have been conducted worldwide on the free-living marine nematodes, they still remain classified as unexplored taxa in Korea. Compared to approximately 7,000 species of free-living marine nematodes recorded worldwide, a small fraction of that (approximately 50 species) have been recorded in Korea. For this PhD thesis, coastal regions of entire Korean peninsula were surveyed over the span of three years (2015-2017) through a project “National Investigation of Marine Ecosystem”. As a result, 5,222 specimen of free-living marine nematodes were examined and identified to genus and/or species level. Identified nematodes belonging to 2 classes, 8 orders, 37 families, 161 genera and 458 species were recorded from coasts of Korea. Selected four genera belonging to families Ironidae and Thoracostomopsidae were reviewed and revised bibliographically along with description of three new species and two unrecorded species. The descriptions are accompanied with revised diagnosis of the respective genera, compiled tabular key consisting of all significant measurements of all valid congeners and new identification key to the genus. In some cases, pictorial key consisting of retraced illustration of head and tail, mtCOI (JB3/JB5) and 18S rRNA (MN18F/22R) sequences and their reflective molecular phylogenetic analysis are provided.