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 Corononema vulgare sp. n. ( Figures 1 and 2 , Table 1 ) Type material . Holotype male, inventory slide number NSS-SH 2, 6; deposited in the Vietnam National Museum of Nature , Vietnam Academy of Science and Technology ( Hanoi , Vietnam ). Paratypes : 10 ♂ , slide number CD-2020-1 ( 4 specimens ) and CD-2020-2 ( 6 specimens ), and 10 ♀ , slide number CD-2020-3 ( 5 specimens ) and CD-2020-4 ( 5 specimens ); 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 reefs from Hon Ba Island , Con Dao Archipelago , Ba Ria-Vung Tau Province . Coordinates : 8038 ʹ52ʹʹN, 106033 ʹ10ʹʹE. Depth : 2m . Water salinity: 32 ‰. Etymology . The specific epithet means “ordinary”, “usual”. Descriptions. Males. Body slender, medium size. Head end narrowed. Cuticle coarse annulated, especially at the anterior body end, annules 1–2 µm, without longitudinal ridges. Somatic setae short and rare, 3–4 µm long. Labia relatively high; labial region well separated from the rest of the body by cuticular mouth ring. Deep groove located between the inner labial setae and outer labial and cephalic setae. Six inner labial setae 2–3 µm long, six outer labial setae 3–5 µm long, four cephalic setae 2–3 µm long. Four cervical setae, 2–3 µm long and located at level of posterior half of pharynx length. Cheilostoma narrow, set off from the pharynx with two strong cuticle rings. Pharyngostoma spacious, in the shape of a short cylinder 8–11 µm long and 6–8 µm wide. Amphidial fovea circular, 4–5µm diameter, and located at 9–11 µm from the anterior body end. Pharynx cylindrical and muscular. Cardia small, triangular, protruding into the lumen of intestine. Cardial glands not observed. Two opposed testes. Anterior testis straight, located to the left of the intestine. Posterior testis curved, short, barely visible. Spicules thin, comparatively short, curved with head. Spicules 25–28 µm long. Gubernaculum surrounds spicule tips, 3 µm long. Precloacal ventromedial supplements absent. FIGURE 1. Corononema vulgaris sp. n. Holotype male and paratype female. A: male, head; B: male, anterior body end; C: spicules and gubernaculum; D: female, posterior body end; E: male, posterior body end. Scale bars: A, C—10 µm; B—80 µm; D—40 µm; E—30 µm. FIGURE 2. Corononema vulgaris sp. n. Holotype male and paratype female. A: male, entire body; B: female, entire body; C: male, anterior body end; D: female, head; E: male, head; F: female, head; G: female, vulva region; H: male, cloaca region; I: male, posterior body end; J: female, posterior body end; K: male, tail end. Scale bars: A, B—100 µm; C—50 µm; D, E, F, H, K—5 µm; G, I, J—20 µm. TABLE 1. Measurements of Corononema vulgare sp. n. All measurements are in µm, except for the ratios a, b, c, cʹ and V.

Character	Holotype male	Paratypes males (n = 10)		Paratypes females (n = 10)
range	mean	range	mean
Length	981	907–969	946	935–1066	1007
a	36	35–45	38	35–39	37
b	2.9	2.8–3.5	3.2	2.9–3.2	3.0
c	12.6	12.6–16.6	14.6	11.0–14.2	12.6
cʹ	4.2	2.9–4.2	3.3	3.6–4.7	4.2
V (%)	–	–	–	81.2–84.5	82.6
Labial region width	10	8–11	9	8–11	10
Outer labial setae length	4	3–5	4.0	3–5	4.0
Cervical setae length	3	2–3	2.5	2–3	2.5
Stoma length	17	15–19	17	16–20	17
Mid-body diameter	27	21–27	25	26–29	27
Anal (cloacal) body diameter	19	18–22	20	18–20	19
Pharynx length	333	272–343	294	298–357	334
Distance from pharynx base to vulva	–	–	–	479–512	498
Distance from vulva to anus	–	–	–	85–114	95
Distance from pharynx base to cloaca	570	561–615	587	–	–
Tail length	78	56–78	65	68–95	80
Spicules length (along arc)	26	25–28	27	–	–

Tail elongated-conical. Annulation at tail end and terminal setae absent. 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 separated from rest of the body by cuticular mouth ring. Six internal labial setae 2–3 µm long; outer labial setae and cervical setae 3–5long; cephalic setae 2–3 µm long. Cheilostoma thin, set off from pharyngostoma with two cuticular rings. Pharingostoma in the shape of short cylinder, 8–10 µm long, 6–8 µm wide. Amphidial fovea circular, located 10–12 µm from anterior body end. Pharynx muscular and equally thickened along its entire length. Ovary single, anterior, straight, relatively long and located to the left of intestine. Vulva post- equatorial, in the form of transverse slit. Vulva lips only slightly protruding from the contours of body. Vagina short, thin-walled and situated obliquely towards the posterior end of the body. Uterus spacious, filled with numerous spermatozoids. Distance from vulva to anus just slightly longer than the tail. Tail elongated-conical. Subterminal setae absent. Caudal glands and spinneret present. Differential diagnosis. At the present, the genus Corononema Nicholas & Stewart, 1995 includes two valid species. Corononema parvum Nicholas & Stewart, 1995 found in the coastal shallow water sea area off the coast of Australia and C. thai Nicholas & Stewart, 1995 found in coastal sea area off the coast of Thailand ( Nicholas & Stewart 1995 ). The new species is morphologically similar to C. thai , but differs from it by the absence of longitudinal ridges on the cuticle (eight longitudinal ridges on the cuticle in C. thai ), shorter outer labial setae (3.0–5.0 µm long vs 6–10 µm long in C. thai ), and a different shape of gubernaculum.