Pselionema huakita, Leduc, 2024

Leduc, Daniel, 2024, Four new free-living marine nematode species (Plectida: Ceramonematidae) and two new species records (Desmodorida: Desmodorinae) from Rangitāhua / Kermadec Islands, Aotearoa / New Zealand, European Journal of Taxonomy 970, pp. 138-174 : 163-165

Pselionema huakita sp. nov.

urn:lsid:zoobank.org:act:31276D59-4875-4ACF-AEB6-F2A7A6CE77B4

Figs 11–12 , Table 3

Diagnosis

Pselionema huakita sp. nov. characterised by body length 900–1259 m, presence of 123–161 body annules, small or indistinct zygapophyses, cephalic setae 0.71–0.93 cbd long, loop-shaped amphids with unequal branches located at middle of cephalic capsule, spicules 29–34 µm long, and tail 9–15 cloacal / anal body diameters long.

Differential diagnosis

The new species is most similar to P. simile (described from the coastal Mediterranean) in body length (about 1000 µm), ratio of a (50–70), and number of body annules (ca 160 or less). The new species differs from P. simile in cephalic capsule length (38–43 vs 25–31 µm in P. simile ), longer cephalic setae (10–15 vs 7–8 µm in P. simile ), longer amphids (16–18 vs 12–14 µm in P. simile ), longer spicules (29–34 vs 27 µm in P. simile ), and greater number of cuticle annules in tail region (24–30 vs 17–20 in P. simile ).

Etymology

‘ Huakita ’are bacteria,which are likely an important food source for this species and other ceramonematids. Māori name ‘ toke huakita ’.

Type material

Holotype NEW ZEALAND • ♂; Kermadec Islands , Raoul Island (off Western Spring); 29.22992° S, 177.96448° W; depth 16 m; 22 Nov. 2021; coarse sand and gravel sediments, voyage TMOR2021 , station 85; NIWA 154949 .

Paratypes NEW ZEALAND • 2 ♂♂, 1 ♀; same data as for holotype; NIWA 154950 • 1 ♂, 1 ♀; Kermadec Islands , Raoul Island (Denham Bay); 29.26302° S, 177.95747° W; depth 15 m; 20 November 2021; sandy sediments, voyage TMOR2021 , station 30; NIWA 154951 .

Type habitat and locality

Shallow subtidal, Raoul Island, New Zealand.

Description

Male

Body colourless, slender, cylindrical, tapering slightly towards posterior extremity. Cuticle coarsely annulated along entire body, except for cephalic capsule and terminal cone. Each annule and terminal cone divided into plates by eight longitudinal crests/ ridges extending from cephalic capsule to terminal cone. Epicristae of each annule slightly overlapping adjacent annules. Zygapophyses small, may be indistinct.Annules unequal in width along body; annule width increasing gradually from first postcephalic annule (6–7 µm, as measured in lateral field) to annule number 29–39 or slightly posterior to ventral gland (10–11 µm), followed by narrower one (7–8 µm); annules then stay roughly equal in size for most of mid-body region until decreasing in width again in precloacal region to about 6 µm in annule immediately anterior to cloaca; this annule followed posteriorly by much wider annule (12–13 µm) then by caudal annules gradually decreasing in width toward terminal cone; last annule before terminal cone is narrowest (ca 5 µm). Caudal annules transversely unequal, usually wider on dorsal side than ventral side. Intracuticular vacuoles absent. Four sublateral cuticle pores present on cephalic capsule; two laterodorsal pores at base of cephalic capsule or at level of posterior edge of amphid, and one dorsal and one ventral pore at level of anterior edge of amphids. Single sublateral cuticle pore also present on first body annule, and other sublateral pores sparsely distributed along rest of body. One cuticle pore observed near tip of terminal cone. Lateral alae absent. Cephalic capsule elongated with rounded lip region; lip region not set off from rest of cephalic capsule. Longitudinal crests extending from base of cephalic capsule to about one third of cephalic capsule length. Inner and outer labial sensilla not observed. Cephalic setae 0.71–0.93 cbd long. Loop-shaped amphids with unequal branches located at middle of cephalic capsule; amphidial aperture of same size and shape as amphidial fovea. Buccal cavity minute or funnel shaped, without differentiation or cuticularisation. Pharynx cylindrical, with relatively weak subdivision into anterior corpus and posterior postcorpus; corpus ca 55% of pharynx length, uniformly cylindrical, muscular; postcorpus ca 45% of pharynx length, also muscular consisting of narrower isthmus followed by short, pear-shaped pharynx. Pharyngeal glands indistinct. Pharyngeal lumen uniform in thickness, tubes and valve-like structures absent. Cardia 5–6 µm long, not surrounded by intestine. Nerve ring surrounding anterior portion of isthmus. Secretory-excretory system present; excretory pore on annule 15–16; ventral gland slightly posterior to cardia.

Reproductive system diorchic with two opposed testes located either both to right or both to left of intestine. Anterior testis outstretched; structure of posterior testis could not be determined. Spicules paired, symmetrical, weakly arcuate, 29–34 µm long. Gubernaculum plate-like, without apophyses. Precloacal seta or spine absent. Caudal glands not observed; spinneret present with apparently three separate outlets immediately posterior to terminal cone. Terminal cone 18–23 µm long.

Female

Similar to males, but with slightly smaller amphids and longer tail with few if any caudal setae. Reproductive system didelphic, amphidelphic, with reflexed ovaries; in one specimen, both ovaries located to left of intestine. Position of ovaries in other specimen could not be determined. Anterior ovary more developed than posterior ovary. Vulva a transverse slit slightly anterior to mid-body. Vagina straight, with thickened walls, surrounded by sphincter muscle. Pars refringens vaginae not observed. Intrauterine egg not seen. First and second postanal annules 10–13 µm wide.

Figures

Fig. 11. Pselionema huakita sp. nov. A. Holotype, ♂ (NIWA 154949). B–F. Paratypes (NIWA 154950- 1). A. Pharyngeal body region. B. ♀, cephalic region. C. ♂, cephalic region. D. ♂, posterior body region. E. ♀, posterior body region. F. ♀, reproductive system. Scale bar: A = 40 µm; B–C = 30 µm; D = 37 µm; E = 44; F = 52 µm.

Fig. 12. Pselionema huakita sp. nov., light micrographs. A–B. Holotype, ♂ (NIWA 154949). C–F. Paratype, ♂ (NIWA 154950). A. Optical section of cephalic region. B. Surface view of cephalic region. C. Optical section showing junction of pharynx and intestine. D. Optical section of cloacal region. E. Surface view of cloacal region. F. Entire male. Scale bar: A–E = 40 µm; F = 85 µm.