Cheironchus haurakiensis, Leduc, Daniel & Zhao, Zeng Qi, 2016

Leduc, Daniel & Zhao, Zeng Qi, 2016, Molecular characterisation of five nematode species (Chromadorida, Selachinematidae) from shelf and upper slope sediments off New Zealand, with description of three new species, Zootaxa 4132 (1), pp. 59-76 : 62-65

Cheironchus haurakiensis n. sp.

( Figures 1 & 2 , Table 1 )

Diagnosis. Cheironchus haurakiensis n. sp. is characterised by cephalic setae 9–12 µm long, multispiral amphids with five turns, lateroventral mandibles 49–61 µm long with central arm curved distally and bearing 4–5 pointed projections, and each palm bearing 4–5 pointed projections, ten precloacal supplements in a 1 + 9 arrangement (posteriormost supplement 60 µm from 2nd posteriormost supplement and remaining supplements 33–43 µm apart), spicules 78 µm long, and blunt conical tail with thickened cuticle.

Etymology. This species is named after the type locality.

Material examined. Holotype male ( NIWA 99777), collected 10 May 2015 ( NIWA cruise TAN 1506, station 45), continental shelf off Hauraki coast, New Zealand (175.1495º E, 35.8243º S); water depth: 127 m. One paratype female ( NIWA 99778), same data as holotype.

Description. Male Body cylindrical, stout. Cuticle 4–5 µm thick, gradually thickening posteriorly in tail region, up to 14 µm thick at posterior extremity ( Fig. 2 B); transverse rows of punctations without lateral differentiation. Anteriormost punctations noticeably smaller on remainder of body. Somatic setae short and sparse, arranged irregularly. Head not set off from body. Mouth opening wide, surrounded by six fleshy, conical lips, each bearing a conical inner labial papilla terminally; labial region surrounded by cuticular fold. Six conical outer labial papillae, ~2 µm long, and four markedly longer cephalic setae (~0.3 cbd) situated in one circle. Amphideal fovea situated near anterior extremity, multispiral with 5.0–5.25 turns and circular outline. Anterior buccal cavity (cheilostom) small, cup shaped, with fine rugae. Posterior buccal cavity (pharyngostom) with three mandibles; lateroventral mandibles well-developed, with central arm and two lateral arms. Central arm curved distally and with four or five inward pointed projections; each palm with broad anterior portion bearing five (four in one case) pointed projections, and thin, pointed posterior portion ( Fig. 1 B, C). Dorsal mandible short and difficult to distinguish, without differentiated anterior tip or palms. Pharynx short, muscular, with large, oval anterior bulb and smaller spherical posterior bulb. Nerve ring situated slightly posterior to middle of pharynx length. Cardia short, 9 µm long, not surrounded by intestinal tissue. Small renette cell present at level of cardia; excretory pore not observed.

Reproductive system diorchic with short outstretched testes ( Fig. 2 C). Anterior and posterior testes both on right of intestine. Sperm cells globular to oval-shaped, ~5-6 × 9–10 mm. Spicules paired, curved, 1.5 cloacal body diameters long, with narrow, strongly curved proximal portion and pointed distal portion. Gubernaculum short, without crurae or apophyses. Mid-ventral row of ten cup-shaped precloacal supplements in a 1 + 9 arrangement; posteriormost and 2nd posteriormost supplements 60 µm apart, distance between other supplements 33–43 mm. Tail short, bluntly conical, with sparse, very short lateral, subventral, and subdorsal setae and three terminal setae. Caudal glands extending slight anterior to cloaca; spinneret present.

Females Similar to male. Reproductive system didelphic-amphidelphic with reflexed ovaries both on right side of intestine. Vulva situated slightly post-median. Proximal portion of vagina surrounded by constrictor muscle.

Species Cheironchus haurakiensis n. sp.

Male Female Holotype Paratype Differential diagnosis. Cheironchus haurakiensis n. sp. differs from most species of the genus except C. vorax in the shape of the tail, which is conical with blister in C. paravorax , conical and gradually tapering in C. conicaudatus , and conicocylindrical in C. dactylocaudatus . C. haurakiensis n. sp. resembles C. vorax in the shape and size of the lateroventral mandibles and spicules, and blunt conical tail, but can be differentiated from the latter in the number and arrangement of precloacal supplements (10 supplements in a 1 + 9 arrangement vs 12–20 regularly-spaced supplements in C. vorax ). C. haurakiensis n. sp. also differs from the original description of C. vorax by Cobb (1917) and re-description by Tchesunov & Okhlopkov (2006) from the western Atlantic coast by the shorter spicules (78 vs 113–125 mm) and higher values of c (32–38 vs 24–29).

Figures

FIGURE 1. Cheironchus haurakiensis n. sp. A: Male anterior body region; B: male head; C: lateroventral mandible; D: spicule and gubernaculum; E: female reproductive system. Scale bar: A = 50 mm, B = 28 mm, C = 20 mm, D = 23 mm, E = 100 mm.

FIGURE 2. Cheironchus haurakiensis n. sp. A: Surface view of female head; B: male posterior body region; C: entire male; D: female posterior body region. Scale bar: A = 40 mm, B = 67 mm, C = 108 mm, D = 295 mm.