Pseudochromadora reathae, Leduc & Wharton, 2010

Leduc, D. & Wharton, D. A., 2010, New free-living marine nematode species (Nematoda: Desmodoridae) from the coast of New Zealand, Zootaxa 2611 (1), pp. 45-57 : 46-52

Pseudochromadora reathae n. sp.

( Fig. 1–4 , Table 1)

Material examined. Holotype Adult male, collected by D. Leduc, January 2007, Harwood (upper intertidal), Otago Harbour, southern New Zealand 45º49’16.57’’S, 170º40’11.53’’E. Unvegetated sandy sediment (85% fine sand, mean grain size = 2.4 phi, sorting coefficient = 0.4 phi) with <1% mud content near stream ( NNCNZ 265 ).

Allotype Adult female, same data as holotype ( NNCNZ 2575 )

Paratypes Two males, two females, two J 4 juveniles, same data as holotype ( NNCNZ 2573-4 , 2576-9 ); two males, two females, same data as holotype ( NIWA 48774 ) .

Description. Males Short (550–665 µm) cylindrical body, golden colour, widest at level of pharyngeal bulb, tapering towards both extremities. Most specimens covered in thick mucus with adhering particles, difficult to remove. Ecto-symbiotic bacteria, 3–5 µm long, observed in most specimens, usually attached to neck region, but also in other parts of body ( Figure 4 B ). Cuticle annulated posterior to head capsule; lateral alae present from posterior to pharyngeal bulb to level of cloaca, extending to tail region in some specimens. Body annuli do not interdigitate at level of lateral alae. Minute, filiform, irregularly spaced spines (not visible under LM) in pharyngeal region, becoming sparser (except on lateral alae) and triangular in shape in main part of body ( Fig. 3 A and 3 E ). Eight longitudinal rows of somatic setae.

Blunt, rounded head, slightly offset in most specimens. Cephalic capsule with very fine groove (sutura) in the cuticle separating lip region from main head region. Main head region usually wider than lip region. Lips often folded inwards ( Fig. 1 E ), sometimes extended ( Fig. 3 B ). Six setiform internal labial papillae, six smaller external labial papillae, and four cephalic setae located on labial region of cephalic capsule. Internal labial papillae inconspicuous unless lips extended. Loop-shaped fovea amphidialis and apertura amphidialis situated on main head region.

Buccal cavity strongly cuticularised with one large dorsal tooth and two small ventrosublateral teeth. Muscular pharynx, always bent. Large oval bipartite oesophageal bulb with strongly cuticularised lumen. Nerve ring inconspicuous, excretory pore not observed.

Reproductive system monorchic with one anterior outstretched testis located on the right or left of intestine. Mature sperm cells globular, 6–7 µm diam. Spicules arcuate with large capitulum, gubernaculum with dorsally directed apophyses. Conspicuous pre-cloacal supplements, consisting of 8–9 cone-shaped structures with a central projection flanked by two cuticularised pieces (in lateral view). Central portion of pre-cloacal supplements consists of a star-shaped structure with six minute pointed projections ( Fig. 3 D ). Conspicuous paired gland cells connect with each supplement, gland openings apparently situated between supplements ( Fig. 3 D ). Tail conical with clear spinneret and three caudal glands. Amorphous material often seen protruding from tail tip.

Females Similar to males, but with unispiral apertura amphidialis and loop-shaped fovea amphidialis. Reproductive system with two reflexed genital branches located on right side of intestine. Vulva located approx. two thirds of body length from anterior. Cuticular vagina vera and vagina uterina surrounded by constrictor muscle. Tail with sparse, short somatic setae.

Fourth stage juveniles Similar to adults but smaller. Unispiral apertura amphidialis. Lateral alae present.

Diagnosis and relationships. Pseudochromadora reathae n. sp. is characterised the combination of the following characters: a cephalic capsule separated into lip and main head regions by a fine sutura, sexual dimorphism in the shape of the apertura amphidialis (loop-shaped in males, unispiral in females), presence of spines on the cuticle, no interdigitation of body annuli at level of lateral alae, eight rows of somatic setae, and conspicuous pre-cloacal supplements consisting of central star-shaped projections flanked by two cuticularised pieces.

P. reathae n. sp. can be distinguished from all other species of the genus by the presence of eight longitudinal rows of somatice setae (compared to six in the other species) and by the presence of 8–9 conspicuous pre-cloacal supplements consisting of star-shaped projections flanked by two cuticularised pieces. P. reathae n. sp. can also be distinguished from most other species (except P. quadripapillata Daday 1899 ) by the absence of interdigitation of body annuli at level of lateral alae.

Etymology. Pseudochromadora reathae n. sp. is named after Reatha Adele Kenny.

Figures

FIGURE 1. Pseudochromadora reathae n. sp. Male. A. Lateral view of neck region. B. Lateral surface view of head. C. Posterior body region showing detail of cuticle in surface view. D. Lateral view of copulatory apparatus. E. Entire male. Scale bar: A, B, C, D = 20 µm; E = 27 µm.

FIGURE 2. Pseudochromadora reathae n. sp. Female. A. Entire female. B. Lateral surface view of head. C. Lateral surface view of head. Scale bar: A = 24 µm; B, C = 20 µm.

FIGURE 3. Pseudochromadora. reathae n. sp. SEM. A. Male anterior body region. B. Lateral view of male head. C. Face view of female head. D. Sub-ventral view of pre-cloacal supplements. E. Detail of cuticle in mid-region of body. (Arrows in D indicate openings of glands) Scale bars: A, B, C, E = 10 µm; D = 5 µm.

FIGURE 4. Pseudochromadora reathae n. sp. SEM. A. Lateral view of female head. B. Lateral view of female neck region showing spines and ecto-symbiotic bacteria. Scale bars: A, B = 10 µm.