Deraionema barbatum, Leduc, 2023

Leduc, Daniel, 2023, New nematode species and genera (Nematoda: Chromadorea) from cold seeps on Hikurangi Margin, New Zealand, European Journal of Taxonomy 856, pp. 1-45 : 23-28

Deraionema barbatum gen. et sp. nov.

urn:lsid:zoobank.org:act:2ACBF50F-E281-48D6-9866-D7ED15F5D3BD

Figs 10–12 , Table 5

Diagnosis

Deraionema barbatum gen. et sp. nov. is characterized by body length 2.1–3.2 mm; outer labial setae 6–8 µm long and cephalic setae 4–5 µm long; short and sparse subcephalic setae present anterior to amphids; sixteen longitudinal rows of subcephalic setae present posterior to amphids, increasing in length posteriorly; pronounced sexual dimorphism in amphid shape: in males, amphideal fovea and aperture form a single, narrow band around the entire circumference of the cephalic region, presumably resulting from the fusion of the left and right amphids, in females, amphids are transversely oval with faint outline; large conical buccal cavity with cuticularized ring (cheilostome) and three transverse cuticularized pieces (pharyngostome); slender, elongated spicules 2.4–3.9 cloacal body diameters long with lateral extensions distally bearing minute spines; gubernaculum long and thin, without apophyses or crurae; conicocylindrical tail 3.3–4.8 cloacal/anal body diameters long.

Etymology

The species name is derived from the Latin ʻ barbatus ʼ meaning ʻbeardedʼ and refers to the longitudinal rows of subcephalic setae.

Material examined

Holotype NEW ZEALAND • ♂; Hikurangi Margin , Uruti South cold seep site; 41.4251° S, 176.3510° E; 1227 m water depth; collected on 13 Jul. 2019; voyage TAN1904, station 61; NIWA154914 .

Paratypes NEW ZEALAND • 2 ♂ ♂; same collection data as for holotype; NIWA 154915 • 1 ♂, 1 ♀; Hikurangi Margin, Uruti South cold seep site; 41.4250° S, 176.3510° E; 1226 m water depth; collected on 13 Jul. 2019; sandy mud (91% silt/clay, mean particle size 24 µm); voyage TAN1904, station 61; NIWA 154916 • 3 ♂ ♂; Mungaroa cold seep site; 41.9378° S, 175.3112° E; 2075 m water depth; collected on 7 Jul. 2019; sandy mud (96% silt/clay, mean grain size 17 µm); voyage TAN1904, station 19; NIWA 154917 .

Type habitat and locality

New Zealand continental slope, Hikurangi Margin, Uruti South and Mungaroa cold seeps.

Description

Male

Body cylindrical, colourless, tapering slightly towards both extremities. Cuticle finely striated, no lateral differentiation. Eight longitudinal rows of short and sparse somatic setae short and sparse. Rounded cephalic region, not set-off from rest of body. Lip region well developed with six inner labial papillae. Six outer labial setae, 20–22% cbd long, situated at same level as four slightly shorter cephalic setae, 13–17% cbd. Up to six additional setae present at same level as outer labial and cephalic setae, either adjacent to outer labial and cephalic setae or halfway between outer labial setae, 4 µm long. Variable number of subcephalic setae (up to 20) present at level of buccal cavity and anterior to amphids, 4–5 µm long. Sixteen longitudinal rows of 12–20 subcephalic setae present beginning immediately posterior to amphids, increasing in length posteriorly, 4–47 µm long. Amphidial fovea a single, continuous narrow band around entire circumference of cephalic region, 5 µm in height, located 0.8–0.9 cbd from anterior body extremity; amphideal aperture narrower than amphideal fovea, 2 µm in height, consisting of a single narrow opening surrounding entire circumference of cephalic region. Buccal cavity large, 26–38 µm deep and up to 19 µm wide, conical; cuticularized ring present at base of cheilostome; wall of pharyngostome lightly cuticularized and with three transverse cuticularized pieces arranged in a broken ring, one in each of the dorsal and ventrosublateral sectors. Pharynx muscular, surrounding most of buccal cavity, without posterior bulb; ducts of pharyngeal glands not observed. Nerve ring located at one third of pharynx length from anterior. Secretory-excretory system usually indistinct; pore located posterior to nerve ring near middle of pharynx, ventral gland not observed. Cardia surrounded by intestine, 18–30 µm long.

Reproductive system diorchic with two opposed and outstretched testes; anterior testis located to the left of intestine and posterior testis to the right of intestine. Sperm cells globular, small, 4–5 × 5–7 µm. Spicules slender, 2.5–3.9 cloacal body diameters long, strongly cuticularised, with rounded lateral extensions distally bearing numerous minute spines. Gubernaculum elongated, thin proximally, without dorsocaudal apophyses or crurae. Precloacal supplements absent. Rectal glands and ejaculatory glands not observed. Tail conicocylindrical, with numerous subventral setae and sparse subdorsal setae, 6–14 µm long, three terminal setae 26–33 µm long. Three caudal glands present.

Female

Similar to males but additional setae absent, rows of subcephalic setae posterior to amphids with fewer (5–8) setae, oval amphids with faint contours, and tail with sparsely distributed setae. Reproductive system with single anterior outstretched ovary located to the left of intestine, mature egg 49 × 101 µm; spermatheca present posterior to vulva. Vulva located at two thirds of body length from anterior body extremity; single vaginal gland present.

Figures

Fig. 10. Deraionema barbatum gen. et sp. nov.A, D, G. Paratype (NIWA154915).B, E. Holotype (NIWA 154914). C, F. Paratype (NIWA154917). A–B. Lateral view of male cephalic region. C. Female cephalic region. D. Male posterior body region. E. Male anterior body region. F. Female posterior body region. G. Copulatory apparatus. Scale bar: A = 50 µm; B = 65 µm; C = 55 µm; D = 140 µm; E = 240 µm; F = 120 µm; G = 70 µm.

Fig. 11. Deraionema barbatum gen. et sp. nov. A. Entire male, holotype (NIWA154914). B. Entire female, paratype (NIWA154917). Scale bar = 250 µm.

Fig. 12. Deraionema barbatum gen. et sp. nov. Light micrographs.A–B, E–F. Paratype (NIWA154915). C–D. Holotype (NIWA154917). A. Male cephalic region showing lips, buccal cavity, pharynx and subcephalic setae. B. Male cephalic region showing amphideal aperture. C. Female cephalic region showing lips, buccal cavity and pharynx. D. Female cephalic region showing amphideal aperture and subcephalic setae. E–F. Copulatory apparatus. Abbreviations: aa = amphideal aperture; gu = gubernaculum; n = amphideal nerve; sp = spicule. Scale bar = 20 µm.