Paramonohystera spinosispicula, 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 : 223-228

Paramonohystera spinosispicula sp. nov.

urn:lsid:zoobank.org:act:960CE6DF-E1BA-412D-97D9-FE0D06A596EB

Figs 5–7 , Tables 2 , 4

Diagnosis

Paramonohystera spinosispicula sp. nov. is characterised by body length 1393–1716 µm, the outer labial setae at same level as, and similar in size to, the four jointed cephalic setae, the four short subcephalic setae located subdorsally and subventrally at level of amphids, and circular amphidial fovea (57–69% cbd in males, 50–57% cbd in females). Males have spicules 3.9–4.4 cloacal body diameters long with distal fifth to quarter swollen and covered in small spines; by the gubernaculum with pointed proximal projections extending along spicules dorsally, laterally and ventrally, and distal end with several small, pointed protuberances. Female reproductive system with spermatheca and a post-vulval sac.

Differential diagnosis

The new species differs from all other species of the genus in the structure of the spicules, which are swollen distally with numerous small spines (vs smooth and lacking spines in all other species). In terms of spicules length, P. spinosispicula sp. nov. is most similar to P. sinica (3.9–4.4 vs 4.0–4.4 cloacal body diameters in P. sinica ), but can be differentiated from the latter by the greater body length (1393–1716 vs 933–1023 μm in P. sinica ), the number of combined cephalic setae and outer labial setae (10 vs 12 in P. sinica ), and shorter tail (cˊ = 4.2–5.2 vs 5.7–6.6 in P. sinica ).

Etymology

The species epithet is derived from the latin ‘ spinosus ’ (= ‘thorny’) and refers to the numerous small thorns on the distal part of the spicules in this species.

Type material

Holotype

NEW ZEALAND CONTINENTAL SHELF • ♂; North Island , east coast off Hawke Bay ; 39.2186° S, 177.4321° E; depth 47 m; 5 Jun. 2023; Alan Orpin leg.; voyage KAH2303, station 16 , sandy mud sediments (92% silt/ clay); NIWA 181625 .

Paratypes

NEW ZEALAND CONTINENTAL SHELF • 3 ♂♂, 4 ♀♀; same data as for holotype; NIWA 181626 .

Description

Males

Body colourless, cylindrical, tapering slightly towards both extremities. Cuticle slightly striated, no lateral differentiation. Eight rows of sparsely distributed somatic setae, 2–4 µm long. Cephalic region set-off by slight constriction at level of amphids; well-developed lip region bearing six small labial papillae. Six outer labial setae, 0.4–0.6 cbd long, in same circle as four jointed cephalic setae of similar length. Four short, 3–4 µm long sucephalic setae present subdorsally and subventrally at level of amphids. Amphidial fovea large, circular, with slightly cuticularised outline and almost entirely surrounded by cuticle striations, ca 0.4–0.5 cbd from anterior extremity. Buccal cavity large, funnel- to barrel-shaped, with cuticularised walls, 7–11 µm deep, 5–6 µm wide, without teeth. Pharynx muscular, anterior portion surrounding buccal cavity, widening gradually posteriorly. Nerve ring located near middle of pharynx. Secretory-excretory system not observed. Cardia ca 12–14 µm long, surrounded by intestinal tissue. Reproductive system with two outstretched testes; anterior testis to the left of intestine, posterior testis to the right of intestine. Sperm cells small, globular to spherical, 3–5 ×4–5 µm. Spicules thin, elongated, 3.9–4.4 cloacal body diameters long, cuticularised along almost entire length; distal fifth to quarter of spicules swollen, less strongly cuticularized, covered in small, dense spines pointing towards spicule’s proximal extremity. Gubernaculum ca 40 μm long, forming sheath surrounding distal quarter of spicules, with pointed proximal projections extending along spicules dorsally, laterally and ventrally; distal end of gubernaculum with several small, pointed protuberances, each with internal duct. Precloacal supplements and seta not observed. Three pairs of ejaculatory glands present slightly anterior to spicules. Tail conicocylindrical with rows of subventral and subdorsal setae, 2–10 μm long; three terminal setae 20–29 µm long. Three caudal glands and spinneret present.

Females

Similar to males but with generally wider cephalic and maximum body diameter, amphidial fovea slightly smaller (as % cbd) and tail with sparse setae. Reproductive system with single outstretched ovary to the left of intestine. Spermatheca present; post-vulval sac 65–87 μm long, 13–20 μm wide. Vaginal glands present. Vulva located near mid-body body or slightly posterior. Pars proximalis vaginae surrounded by constrictor muscle.

Figures

Fig. 5.Paramonohystera spinosispicula sp. nov.A, C–D. Paratype, ♀ (NIWA 181626). B, E–F. Holotype, ♂ (NIWA 181625). A–B. Cephalic region. C. Anterior body region. D–E. Posterior body region. F. Specular apparatus. Scale bar: A–B = 20 μm; C = 85 μm; D = 95 μm; E = 65 μm; F = 45 μm.

Fig. 6. Paramonohystera spinosispicula sp. nov. A. Entire paratype, ♂ (NIWA 181626). B. Entire paratype, ♀ (NIWA 181626). Scale bar = 200 μm.

Fig. 7. Paramonohystera spinosispicula sp. nov., light micrographs. A–C. Cephalic region of paratype, ♂ (NIWA 181626). D–E. Spicular apparatus of holotype, ♂ (NIWA 181625). Scale bar: A–C = 10 μm; D–E = 11 μm.