Pseudocheironchus ingluviosus, Leduc, 2013

Leduc, Daniel, 2013, Two new genera and five new species of Selachinematidae (Nematoda, Chromadorida) from the continental slope of New Zealand, European Journal of Taxonomy 63, pp. 1-32 : 11-14

Pseudocheironchus ingluviosus gen. et sp. nov.

Figs 4-7 , Table 1

urn:lsid:zoobank.org:act:258E6E4A-6142-4A49-88B9-9A6E9B765309

Diagnosis

Pseudocheironchus ingluviosus gen. et sp. nov. is characterised by mandibles, each with two pairs of four blunt hooks, mandibles joined by a membrane with slender cuticularised ridges at their junction, multispiral amphideal fovea with 5.0 turns, short conical tail with rounded end, and males with spicules 1.5-1.7 abd long and 17-19 cup-shaped pre-cloacal supplements.

Etymology

The species name comes from the Latin ingluviosus (= voracious, gluttonous), and refers to the welldeveloped feeding apparatus of the species.

Material examined

Holotype

NEW ZEALAND: ♂, NIWA 88356 , 5 Apr. 2007, NIWA cruise TAN0705, station 38, western Chatham Rise crest, 43.8266° S, 176.7043° E, 478 m, medium sand (45.3%), fine sand (43.9%).

Paratypes

NEW ZEALAND: 1 ♀, NIWA 88357, 20 Feb. 2011, NIWA cruise TAN1103, station 69, central Chatham Rise, 43.331° S, 178.288° E, 350 m, sediment depth 1-5 cm, mean grain size 55-59 μm, 55-57% sand, particle sorting (geometric) 4.1-4.3. 1 ♂, 1 ♀, NIWA 88358, 5 Oct. 2001, NIWA cruise TAN0116, station U2582, Chatham Rise crest, 43.4333° S, 178.5000° E, 350 m, silt/clay (37.5%), fine sand (23.4%), medium sand (21.4%).

Description

Males

Body cylindrical, tapering slightly towards both extremities. Cuticle 1.5-1.8 μm thick throughout body, thicker in tail region, 3-4 μm, with transverse rows of punctations, without lateral differentiation or differentiation consisting of slightly larger punctations. Somatic setae short and sparse, in four sublateral rows. Head slightly set off by constriction at level of amphid. Six conical inner labial papillae; six small outer labial setae and four slightly longer cephalic setae (~ 0.1 cbd) situated in one circle. Amphideal fovea situated near anterior extremity, multispiral with 5.0 turns and transversely oval outline. Anterior portion of buccal cavity short, with six pairs of thin, cuticularised rhabdions fused proximally, ~ 6 μm long. Posterior buccal cavity with three equal mandibles, 18-21 μm long, with one mandible situated dorsally and two sub-ventrally. Each mandible consists of a heavily cuticularised axis with a longitudinal groove ( Fig. 5A ); axis is thinnest in middle portion and widens towards the posterior and anterior extremities; anterior portion consists of two sets of four blunt hooks; posterior extremity of axis rounded. Two thin membranes extend laterally from the entire length of each mandible (often difficult to observe); a thin, slightly bent, cuticularised ridge is found at the junction of the membranes, one situated ventrally and two sub-dorsally ( Fig. 5A, B ). Pharynx short, with conspicuous oval-shaped anterior bulb surrounding posterior portion of buccal cavity, 23 μm wide, 29 μm long, and rounded posterior bulb, 25 μm wide. Nerve ring at middle of pharynx. Secretory-excretory (S-E) system present, cellular body of ventral gland situated ~ 1.5 cbd posterior to pharynx, pore situated near posterior extremity of posterior pharyngeal bulb. Intestine cells with numerous round inclusions, most dense in cells immediately posterior to pharynx ( Fig. 4A ).

Reproductive system diorchic with short, ~ 50 μm long, outstretched testes. Anterior testis on left of intestine, posterior testis on right of intestine. Small, nucleated sperm cells, oval or elongated with pointed ends, ~ 6 × 2 μm. Spicules paired, curved, 1.5-1.7 abd long, widest in middle portion and tapering distally. Gubernaculum small, slightly bent, median part (cuneus) with hook-shaped projection pointing dorsally ( Fig. 4F ). Three, perhaps four pairs of ejaculatory glands situated anterior to spicules ( Fig. 4E ). Mid-ventral row of 17-19 cup-shaped pre-cloacal supplements, ~ 5 μm wide and 5 μm deep, situated 5-8 μm apart. Pre-cloacal supplements thickly cuticularised, with nerve entering anterior side of cup. No pre-cloacal seta observed. Post-cloacal setae/papillae not observed. Tail short, conical, with rounded posterior extremity and three small terminal setae. Three caudal glands and small spinneret present.

Females

Similar to males, but with smaller amphideal fovea with circular outline. Reproductive system didelphic-amphidelphic with reflexed ovaries. Anterior ovary on left of intestine, posterior ovary on right of intestine. Vulva located slightly pre-median. Vaginal glands present, pars proximalis vaginae surrounded by constrictor muscle.

Figures

Fig. 4. Pseudocheironchus ingluviosus gen. et sp. nov. A. Lateral view of anterior body region of male. B. Sublateral view of anterior body region of female. C. Surface view of female head. D. Surface view of male head. E. Male posterior body region. F. Spicule and gubernaculum. G. Female posterior body region. Arrow shows location of ejaculatory glands. Scale bar: A-B = 25 μm; C-D = 15 μm; E, G = 62 μm; F = 10 μm.

Fig. 5. Pseudocheironchus ingluviosus gen. et sp. nov. A. En face and side views (left and right, respectively) of mandibles. B. Sub-lateral view of female head showing position of mandibles and cuticularised ridges. a = mandible axis; m = membrane; r = cuticularised ridge; t = teeth. Scale bar: A = 10 μm; B = 20 μm.

Fig. 6. Pseudocheironchus ingluviosus gen. et sp. nov. A. Entire male. B. Entire female. Scale bar = 100 μm.

Fig. 7. Pseudocheironchus ingluviosus gen. et sp. nov. Light micrographs. A. Female head region showing buccal cavity and mandibles. B. Female posterior pharyngeal bulb and anterior portion of intestine. C. Male posterior body region showing right spicule and cup-shaped supplements. D. Detail of pre-cloacal supplements. Scale bar: A-C = 30 μm; D = 10 μm.