Abstract
During a survey of the free-living marine nematodes of Korea, two species belonging to the genus Oncholaimus Dujardin, 1845 were discovered. A new species, Oncholaimus tripapillatus sp. nov. and a newly recorded species, Oncholaimus qingdaoensis Zhang & Platt, 1983, are reported. Oncholaimus tripapillatus sp. nov. was collected from the washing of subtidal coarse sediments around Dokdo Island of the East Sea, Korea. Oncholaimus tripapillatus sp. nov. is characterized by a relatively long (4071–4435 µm in males and 4514–4661 µm in females) and slender body, a slightly constricted head region, relatively long cephalic setae (10–12 µm), males having a precloacal sexual protuberance bearing two small cone-shaped supplementary spines, five pairs of long cloacal setae (three pairs of precloacal and two pairs of postcloacal setae in subventral position), and three remarkable papillae near the end of the tail, with two pairs of subventral setae. The Korean specimens of Oncholaimus qingdaoensis Zhang & Platt, 1983 are almost identical to the Chinese specimens of the original description from the intertidal sand of Qingdao, China. However, the Korean specimens differ from the Chinese specimens in the longer body length in males (3379–3715 µm vs. 2380–2640 µm), the larger spicule length (47–52 µm vs. 34–36 µm), and the presence of ventral tail papillae situated around 14–16 µm from the tail tip. Detailed morphological features and illustrations of two Oncholaimus species from Korea were obtained by differential interference contrast microscopy and scanning electron microscopy. A pictorial key to the species group with distinct tail papillae among the genus Oncholaimus is also provided.
Highlights
The genus Oncholaimus Dujardin, 1845 is distinguished from the other genera of the family by the presence of the largest left ventrosublateral tooth, relatively short spicules, and a monodelphic–prodelphic reproductive system in females [1]
During a continuous ecological investigation on the biodiversity of the free-living marine nematodes around Korean waters, we found two Oncholaimus species from the intertidal and subtidal sediments of the eastern, southern, and western coasts of Korea
The marine nematodes were obtained from the upper surface of the intertidal sediment from the southern and western coasts of Korea using a hand scoop, as well as by means of a Smith–McIntyre grab from the shallow subtidal benthic environment sediment of Dokdo
Summary
The genus Oncholaimus Dujardin, 1845 is distinguished from the other genera of the family by the presence of the largest left ventrosublateral tooth, relatively short spicules, and a monodelphic–prodelphic reproductive system in females [1]. The genus Oncholaimus shows worldwide distribution and occurs in various habitats, from littoral sediment to brackish water and deep-sea environments [2,3]. & Belogurova, 1978) from Shikotan Island, Kuril Islands, and its adjacent Russian waters of the East Sea (Sea of Japan) [5,6,7,8]; two species Only one Oncholaimus species, O. secundicollis, has been reported from the rocky intertidal seagrass habitat on the eastern coast of Korea [10,14]. During a continuous ecological investigation on the biodiversity of the free-living marine nematodes around Korean waters, we found two Oncholaimus species from the intertidal and subtidal sediments of the eastern, southern, and western coasts of Korea. We provide a pictorial key and a comparison table of the diagnostic morphological characteristics of the species within the genus Oncholaimus with distinct tail papillae in the tail region
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