Psammonema buamphida, Leduc, 2025

Leduc, Daniel, 2025, New nematode species (Nematoda: Chromadorea) and records from the New Zealand continental shelf, European Journal of Taxonomy 981, pp. 213-238 : 217-222

Psammonema buamphida sp. nov.

urn:lsid:zoobank.org:act:3E6715A8-EA41-480C-8B95-0AC2342AE26D

Figs 2–4 , Tables 2–3

Diagnosis

Psammonema buamphida sp. nov. is characterised by a body length of ca 840–1020 µm, the lateral alae extending from posterior to pharynx to beyond cloaca/ anus, eight longitudinal rows of alternating long and short somatic setae, the main portion of cephalic capsule with vacuoles, the lip region set off from main portion of cephalic capsule by sutura, the large cryptospiral amphidial fovea (69–79% cbd wide) and an unispiral amphidial aperture, no sexual dimorphism in the amphidal fovea shape or size, a pharyngeal bulb without conspicuous partitions; by the absence of thorns in females, and the absence of precloacal supplements, copulatory or postcloacal thorns in males.

Differential diagnosis

The new species differs from the other three species of the genus in having large cryptospiral amphidial fovea in both males and females (sexual dimorphism in amphidial fovea shape and size present in other species) and females having only one type of somatic setae (instead of two or three types in the other species).

Etymology

The species epithet is derived from the latin prefix ‘ bu- ’ (= ‘large’, ‘huge’, ‘great’) and refers to the large size of the amphidial fovea in both sexes of this species.

Type material

Holotype

NEW ZEALAND CONTINENTAL SHELF • ♂; North Island , east coast off Poverty Bay ; 38.7641° S, 178.1942° E; depth 54 m; 16 Jun. 2023; Alan Orpin leg.; voyage KAH2303, station 66 , sandy mud sediments (83% silt/ clay); NIWA 181622 .

Paratypes

NEW ZEALAND CONTINENTAL SHELF • 2 ♂♂, 2 ♀♀; same data as for holotype; NIWA 181623 • 1 ♂, 2 ♀♀; Tokomaru Bay ; 38.1316 ° S, 178.5839° E; depth 42 m; 16 Jun. 2023; Alan Orpin leg.; voyage KAH2303, station 45 , sandy mud sediments (77% silt / clay); NIWA 181624 .

Description

Males

Body short, stout, cylindrical, with slight golden-brown colouration, tapering slightly towards anterior and posterior extremities. Cuticle 4–5 μm thick, with ca 2 μm wide annulations; lateral alae extending from level of cardia or slightly further posterior to cardia to slightly posterior to cloaca, cuticle annulations sometimes interdigitate at level of lateral alae depending on angle of specimen. Eight longitudinal rows of somatic setae present, 7–16 μm long setae (longest in posterior half of body) alternating with shorter 2–4 μm long setae. Blunt, truncated cephalic region not offset from rest of body. Non-annulated cephalic capsule 16–29 μm wide, 26–33 μm high, with main portion surrounded by slightly thickened cuticle with numerous small vacuoles; lip region separated from main portion of cephalic capsule by fold in cuticle (sutura), may be extended anteriorly. Circle of six conical inner labial papillae surrounding buccal opening followed by circle of six slightly smaller outer labial papillae located slightly further posteriorly on lip region. Four short cephalic setae, ca 0.1–0.2 cbd long, at level of sutura and anterior edge of amphidial fovea. Amphidial fovea large, cryptospiral, located on main portion of cephalic capsule. Amphidial aperture unispiral; aperture width narrowest anteriorly and widest posteriorly. Mouth opening surrounded by cuticular folds (cheilorhabdia). Buccal cavity medium-sized, with large, conspicuous, cuticularised dorsal tooth and two smaller ventrosublateral teeth; ring of 8–10 denticles spanning both ventrosublateral sectors either side of the ventrosublateral teeth. Ducts of pharyngeal glands not observed. Pharynx muscular, lumen not cuticularised; anterior portion surrounding buccal cavity, slightly swollen. Posterior pharyngeal bulb present, 52–62 µm long, without conspicuous partitions. Nerve ring located near middle of pharynx. Secretory-excretory system not observed. Cardia short, 8–10 μm long, not surrounded by intestinal tissue. Reproductive system with single outstretched testis located to the right of intestine; sperm cells globular or spherical, 9–19×14–26 µm. Spicules short, 1.4–1.5 cloacal body diameters long, arcuate, with swollen proximal portion (capitulum); velum not observed. Bent or curved gubernaculum without apophyses, ca 35–45% of spicule length, flanking spicules distally. Precloacal supplements not observed; copulatory and postcloacal thorns absent. Tail conical, with 4–12 μm long subventral and subdorsal setae. Three caudal glands and spinneret present. Non-annulated tail tip 19–22 μm long.

Females

Similar to males but with slightly lower values of a (14–15 vs 15–18 in males) and slightly higher values of c (10–11 vs 7–9 in males). Reproductive system with two opposed and reflexed ovaries located ventrally relative to intestine. Mature eggs and spermatheca not observed. Vulva located slightly posterior to mid-body. Cuticular pars distalis vaginae.

Figures

Fig. 2. Psammonema buamphida sp. nov. A–B. Paratype, ♀ (NIWA 181623), cephalic region. C. Holotype, ♂ (NIWA 181622), anterior body region. D. Paratype, ♂ (NIWA 181623), cephalic region. E. Paratype, ♀ (NIWA 181623), posterior body region. F. Holotype, ♂ (NIWA 181622), posterior body region. Scale bar: A–B, D = 20 μm; C = 40 μm; E = 50 μm; F = 35 μm.

Fig. 3. Psammonema buamphida sp. nov. A. Entire holotype, ♂ (NIWA 181622). B. Entire paratype, ♀ (NIWA 181623). Scale bar = 100 μm.

Fig. 4. Psammonema buamphida sp. nov., light micrographs. A–C. Cephalic region of paratype, ♀ (NIWA 181623). D. Entire paratype, ♀ (NIWA 181624). E. Entire holotype, ♂ (NIWA 181622). Scale bar: A–C = 20 μm; D–E = 70 μm.