Corononema vulgare sp. n. and Hofmaenneria coralis sp. n. (Nematoda, Monhysterida) from coral reefs off the coast of Vietnam Author Phuong, Nguyen Thi Xuan 0000-0001-8911-014X Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam. & Graduate University of Science and Technology, Vietnam Academy of Sciences and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam. & ntxphuong. iebr @ gmail. com; https: // orcid. org / 0000 - 0001 - 8911 - 014 X ntxphuong.iebr@gmail.com Author Long, Phan Ke 0000-0003-4998-260X Vietnam National Museum of Nature, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam. & Graduate University of Science and Technology, Vietnam Academy of Sciences and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam. & pkelong @ gmail. com; https: // orcid. org / 0000 - 0003 - 4998 - 260 X pkelong@gmail.com Author Thanh, Tran Thi Viet 0000-0002-2381-5873 Vietnam National Museum of Nature, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam. & thanhbttnvn @ gmail. com; https: // orcid. org / 0000 - 0002 - 2381 - 5873 & Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Yaroslavl Province, Borok, 152742, Russia. Laboratory of Coastal Benthic Ecology, P. P. Shirkov Institute of Ecology, Russian Academy of Sciences, Russia. & gagarin @ ibiw. yaroslavl. ru; https: // orcid. org / 0009 - 0003 - 4817 - 8238 & vadim @ ocean. ru; https: // orcid. org / 0009 - 0003 - 2873 - 0638 thanhbttnvn@gmail.com Author Tu, Nguyen Dinh 0000-0002-1829-3636 Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam. & Graduate University of Science and Technology, Vietnam Academy of Sciences and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam. & ngdtu @ yahoo. com; https: // orcid. org / 0000 - 0002 - 1829 - 3636 ngdtu@yahoo.com text Zootaxa 2023 2023-11-28 5380 1 67 76 https://mapress.com/zt/article/download/zootaxa.5380.1.5/52359 journal article 10.11646/zootaxa.5380.1.5 1175-5326 10212692 1F31D83F-BDFD-4832-8858-4F9A0A0ACA8A Hofmaenneria coralis sp. n. ( Figures 3 and 4 ; Table 2 ) Type material . Holotype male, inventory slide number MSS-SH 1, 2; deposited in the Vietnam National Museum of Nature , Vietnam Academy of Science and Technology ( Hanoi , Vietnam ) . Paratypes : 10 ♂ , slide number CD-2020-7 ( 6 specimens ) and CD-2020-8 ( 4 specimens ), and 7 ♀ , slide number CD-2020-9; deposited in the collection of nematodes of the Institute of Ecology and Biological Resources , Vietnam Academy of Science and Technology ( Hanoi , Vietnam ) . Type locality . Shallow area off the coast of Vietnam . Coral reef from Con Son Island , Con Dao Archipelago , Ba Ria-Vung Tau Province . Coordinates : 8038 ʹ53ʹʹN, 106034 ʹ51ʹʹE. Depth : 1.8 m . Water salinity: 35 ‰. Etymology . The specific epithet means “coral”. Descriptions. Males. Body thin, medium size. Cuticle strongly annulated. Both anterior and posterior body ends narrowed. Cuticle setae numerous, 5–7 µm long. Labial region not separated from the rest of the body. Six internal labial sensillae in the shape of papillae; six outer labial sensillae and four cephalic sensillae in the shape of thin setae, arranged in two circles. Outer labial setae 12–15 µm long, approximately equal to the width of labial region. Cephalic setae 8–10 µm long. Cheilostoma well-developed, spacious, and set off from pharyngostoma by a cuticular ring. Gymnostoma in the shape of short and wide cylinder with cuticularised walls, 3µm long and 6µm wide. Two small denticles at the gymnostoma. Stegostoma funnel-shaped, with thick walls. Amphidial fovea in the shape of ring 5.0–6 µm diameter and located 18–22 µm from anterior body end. Pharynx muscular, equally thickened along its entire length. Cardia small, protruding into the lumen of the intestine. Testis single, straight, located to the right of the intestine. Spicules comparatively short, strongly curved; with heads, 30–34 µm long. Gubernaculum thin, straight, 10–12 µm long. Tail long, gradually narrowing. Caudal setae 5–7 µm long; terminal setae 9 µm long; subterminal setae 17–19 µm long. Caudal glands and spinneret present. Females. General morphology similar to that of males. Structure of cuticle and anterior body end as in males. Cuticle annulated. Labial region not separated from the rest of the body. Six internal labial sensillae in the shape of papillae. Six outer labial sensillae and four cephalic sensillae in the shape of thin setae. Outer labial setae 13–15 µm long; cephalic setae 8–10 µm long. Cheilostoma obvious, set off from pharyngostoma by a cuticular ring. Gymnostoma in the shape of a short and thin cylinder with strong cuticular walls. Amphidial fovea circular, with 4.0 µm diameter and located 19–24 µm from anterior body end. Pharynx cylindrical, muscular. Cardia small. Cardial glands not observed. Reproductive system monodelphic, prodelphic. Ovary comparatively long and located subventrally on the right side of the intestine. Vulva postequatorial, in the form of transverse slit. Vulva lips not sclerotized. Vagina short, with thin walls and sloping towards the posterior body end. Uterus spacious, filled with numerous sperms. Posterior uterus sack and postvulval gland cell not observed. Tail long, gradually narrowing. Caudal setae 5–7 µm long; terminal setae 8–9 µm long. Caudal glands and spinneret present. Differential diagnosis. At present the genus Hofmaenneria Gerlach & Meyl, 1957 includes 11 valid species ( Gagarin & Naumova 2022 ). The new species morphology is close to H. niddensis Gerlach & Meyl, 1957 and H. optata Alekseev, 1983 . It differs from the first species by the thinner body ( a = 44–56 vs a = 35–44 in H. niddensis ), shorter and less slender tail ( c = 7.0–12.6, cʹ = 5.0–8.2 vs c = 4.8–6.1, cʹ = 8.3–9.7 in H. niddensis ), and shorter spicules (30–34 µm long vs 36 µm long in H. niddensis ) ( Gerlach & Meyl 1957 ). H. coralis sp. n. differs from the second species by the longer body ( ♂♂ L = 1046–1293 µm, ♀♀ L = 1172–1202 µm vs ♂♂ L = 920 µm, ♀♀ L = 890–910 µm in H. optata ), comparatively thinner body in females ( ♀♀ a = 46–56 vs ♀♀ a = 28–37 in H. optata ), comparatively shorter pharynx ( ♂♂ b = 5.4–6.7, ♀♀ b = 5.7–6.3 vs ♂♂ b = 4.6, ♀♀ b = 3.8–3.9 in H. optata ), comparatively shorter tail ( ♂♂ c = 9.8–12.6, ♀♀ c = 7.0–10.8 vs ♂ c = 6.7, ♀♀ c = 6.0– 6.4 in H. optata ) and longer outer labial setae ( ♂♂ 12–15 µm vs ♂♂ 8–10 µm in H. optata ) ( Alekseev 1983 ).