Two new species of nematodes from shallow and deep-water sediments in the South China Sea Author Huang, Mian Laboratory of Marine Organism Taxonomy and Phylogeny, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China & Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China & University of Chinese Academy of Sciences, Beijing 100039, China Author Shi, Benze Laboratory of Marine Organism Taxonomy and Phylogeny, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China & Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China & Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China Author Wang, Chunguang Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China Author Xu, Kuidong Laboratory of Marine Organism Taxonomy and Phylogeny, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China & Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China & University of Chinese Academy of Sciences, Beijing 100039, China & Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China text Zootaxa 2021 2021-08-09 5016 4 490 502 journal article 10.11646/zootaxa.5016.4.2 1175-5326 5222467 AB86B403-953C-48E4-9A03-BF9DCE7DAC9A Gomphionema setiforme sp. nov. ( Figs 1–3 ; Table 1 ) Diagnosis. Body small, 716–902 μm long, a=18.7–22.6; cuticle punctated without lateral differentiation and cu- ticular pores; cephalic sensilla about 2 μm long; spiral amphid in 4 turns; cuticularized buccal cavity about 20 μm long, with a large and cuticularized dorsal tooth; pharynx with posterior bulb, 130-141 μm long; tail conical, 55-66 µm long; spicules curved, about 28 μm long; gubernaculum knife-like without dorsal apophysis; and 11 cup-shaped precloacal supplements. Type material. Holotype : one male on slide MBM286822 . Paratypes : one female on MBM286823 , two females and one juvenile on MBM286824 , and one female on MBM286825 . Type locality and habitat. Intertidal zone in the South China Sea ( 23°25'34''N , 116°51'15''E ), where the species was found from muddy sediment in Laichang Ferry of Shantou City , Guangdong Province . Etymology. The Latin adjective setiformis (bristle-like) refers to the cephalic setae, a main feature of the species. Description. Body cylindrical over most of its length, tapering on tail end, 716–902 μm long. Cuticle with regular transverse rows of small punctations from the level of buccal cavity to tail end, lateral differentiations absent ( Figs 1A , 2B ). Somatic setae and cuticular pores not seen. Lip region more or less rounded, confluent with body. Outer and inner labial sensilla papilliform ( Figs 1A , 2A ). Four cephalic sensilla setiform, about 2 µm long. Spiral amphideal fovea in four turns, located close to anterior end of body ( Fig. 1A ). Buccal cavity about 20 µm long, with a large and heavily cuticularized dorsal tooth; composed of a spacious anterior cyathiform chamber with 12 rugae (ribs) and an elongate posterior chamber with cuticularized walls. Pharynx asymmetrical and muscular, 130–140 µm long, posterior portion with a distinct bulb and a hollow muscle cavity ( Figs 1A , 2A ). Cardia small, broadly conoid. Ventral gland sac-like, just behind the base of pharynx. Tail curved ventrally, 55-66 µm long, conoid with rounded end. Caudal glands and spinneret well developed. Male . Reproductive system diorchic, with two opposed, outstretched testes. Anterior and posterior testes on the left and right sides of intestine, respectively. Spicules curved, slightly S-shaped, about 28 µm long, gubernaculum knife-like, without dorsal apophysis ( Figs 1B , 2C, D ). One small seta and 11 cup-shaped supplements situated in front of cloaca. Precloacal supplements extending for 27 µm to 225 µm from cloaca towards anterior end, spacing of supplements slightly increased anteriorly ( Figs 1D , 2D ). Females. Reproductive system didelphic, two ovaries opposed, reflexed ( Figs. 1E , 3B ). Anterior ovary on the right side of intestine, and posterior one on the left side. Vulva in posterior body portion near mid-body. Lips of vulva slightly protruded. Vagina cuticularized, about 0.3 times vulval body diameters long. Uterus spacious. Spermathecae not observed. Juvenile. Similar to male and females in most morphological characters except for smaller morphological measurements. Differential diagnosis and discussion. The genus Gomphionema contains only four species ( Gagarin & Thanh, 2009 ; Bezerra et al ., 2018), among which Gomphionema compactum Gerlach, 1957 was described from a juvenile and thus is not recognized as valid. Gomphionema setiforme sp. nov. is most similar to G. parvum Gagarin & Thanh, 2009 , in particular in the absence of lateral differentiation of cuticle and cuticular pores. However, the new species differs distinctly from the latter by its setiform cephalic sensilla (vs. papilliform), S-shaped spicules (vs slightly arched) and the lower number of precloacal supplements (11 vs. 18–21). Both Gomphionema fellator Wieser & Hopper, 1966 and G. typicum Wieser & Hopper, 1966 have lateral differentiation and cuticle pores (vs. present) and have longer spicules (36–38 µm and 41 µm, respectively vs. 28 µm) and more precloacal supplements (15 and 22, respectively vs. 11).