Ceramonema taikoraha, 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 : 145-150

Ceramonema taikoraha sp. nov.

urn:lsid:zoobank.org:act:4839352A-7414-4D01-B124-5F2E10D743C0

Figs 2–4 , Table 1

Diagnosis

Ceramonema taikoraha sp. nov. is characterised by body length 1380–1428 µm, presence of 161–177 body annules, presence of intracuticular vacuoles, conspicuous zygapophyses, absence of precloacal spine, cephalic setae 0.38–0.50 cbd long in males and 0.32 cbd long in female, medium-sized loop-shaped amphids that are slightly shorter in females than in males, cloacal annule not formed by fusion of contiguous body annules, and gubernaculum with narrow dorsal apophyses.

Differential diagnosis

The new species belongs to Group 1 (species with distinct zygapophyses) and is most similar to Ceramonema taiora sp. nov., C. salsicum (described from the Bay of Biscay, NE Atlantic), and C. africana (described from the coast of South Africa) in having cuticle ornamentation with distinct zygapophyses, body length greater than 700 µm, ratio of a <70, cephalic setae ca ⅓ of cephalic capsule length or less, and cephalic capsule with intracuticular vacuolisation. Ceramonema taikoraha sp. nov. differs C. taiora sp. nov. by greater body length (1380–1428 vs 1040–1141 µm in C. taiora sp. nov.), higher ratio of a (49–60 vs 32–36 in C. taiora sp. nov.), higher ratios of b and c (7–8 vs 4–6 in C. taiora sp. nov.), higher number of body annules (161–177 vs 119–127 in C. taiora sp. nov.), cloacal annule morphology (two unfused contiguous body annules vs fused annules in C. taiora sp. nov.), shorter amphids (16–18 vs 19–26 µm in C. taiora sp. nov.), and absence of precloacal spine (vs present in C. taiora sp. nov.). The new species differs from C. salsicum by the greater body length (1380–1428 vs 960 µm in C. salsicum ), higher ratio of a (49–60 vs 38 in C. salsicum ) and c (7 vs 5 in C. salsicum ), and shorter tail (8–9 vs 10 cloacal body diameters long in C. salsicum ). The new species differs from C. africana in greater body length (1380–1428 vs 1029–1090 µm in C. africana ), higher ratio of b (7–8 vs 5–6 in C. africana ), and longer amphids (in males: 18 vs 10–15 µm; in females: 16 vs 9 µm). The new species is also characterised by a somewhat greater ratio of a (49–60 vs 35–49 in C. africana ) and a somewhat longer cephalic capsule (33–37 vs 27–33 in C. africana ).

Ceramonema taikoraha sp. nov. is also similar to C. inguinispina (described from the Gulf of California) in having body length greater than 700 µm, ratio of a <70, cephalic setae ca ⅓ of cephalic capsule length or less, and cephalic capsule with intracuticular vacuolisation but differ in cuticle ornamentation (distinct vs small zygapophyses in C. inguinispina ), greater body length (1380–1428 vs 822–1154 µm in C. inguinispina ), longer tail (186–206 vs 109–168 µm in C. inguinispina ), amphid shape in females (loop-shaped vs unispiral in C. inguinispina ), shorter amphids (16–18 vs 5–14 µm in C. inguinispina ), and absence of precloacal spine (vs present in C. inguinispina ). The new species also possesses a somewhat longer cephalic capsule (33–37 vs 24–33 µm in C. inguinispina ).

Etymology

‘ Taikoraha ’ are tidal movements over shallow expanses of sediments. Like other ceramonematids, this species of nematode worm (‘ toke ’) possesses thick interlocking cuticle plates to withstand the strong currents of the tide (tai) in the coarse sediments (‘ koraha ’) where it lives. Māori name ‘ toke taikoraha ’.

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 154943 .

Paratypes NEW ZEALAND • 2 ♂♂, 1 ♀; same data as for holotype; NIWA 154944 .

Type habitat and locality

Shallow subtidal, Raoul Island, New Zealand.

Description

Male

Body almost colourless, with slight golden colouration, cylindrical, slightly wider in pharyngeal region than in mid- and posterior body region and tapering slightly towards posterior extremity. Cuticle coarsely annulated along entire body, except for smooth cephalic capsule and terminal cone. Each annule divided into plates by eight longitudinal crests /ridges extending from cephalic capsule to terminal cone. Epicristae of each annule slightly overlapping adjacent annules. Zygapophyses conspicuous. Annules unequal in width and often wider dorsally than ventrally; annule width increasing gradually from first postcephalic annule (6–7 µm, as measured in lateral field) to annule number 28–32 or slightly posterior to ventral gland (10–11 µm), followed by much narrower one (6–7 µm); annules then widen slightly (7–8 µm), and stay roughly equal in size for most of mid-body region until decreasing in width again in precloacal region to about 5 µm in annule immediately anterior to cloaca; this annule followed posteriorly by wider annule (8 µm) then by caudal annules gradually decreasing in width toward terminal cone; last annule before terminal cone is narrowest (3–4 µm). Intracuticular vacuoles occurring within posterior part of cephalic capsule and within body annules. Cuticle pores present; one usually observed on terminal cone (variable position) and one on left or right side of cephalic capsule at level of anterior edge of amphidial fovea and slightly dorsally to the latter. Lateral alae absent. Cephalic capsule elongated, longer than wide, cylindrical with rounded lip region not set off by any constriction. Longitudinal crests extending from base of cephalic capsule to about level of base of cephalic setae. Inner labial sensilla not observed. Outer labial setiform, slightly shorter than, and located anterior to, cephalic setae (0.38–0.50 cbd); cephalic setae located slightly anterior to amphids. Loop-shaped amphids located near middle of cephalic capsule; amphidial aperture slightly shorter than amphidial fovea. Buccal cavity small, funnel shaped, without differentiation. Pharynx cylindrical, distinctly subdivided into anterior corpus and posterior postcorpus; corpus ca 60% of pharynx length, uniformly cylindrical, muscular, with evenly distributed myofilaments; postcorpus ca 40% of pharynx length, also muscular consisting of anterior narrower isthmus and pear-shaped basal swelling. Pharyngeal glands indistinct. Pharyngeal lumen uniform in thickness, tubes and valve-like structures absent. Cardia 10–12 µm long, partially surrounded by intestine. Nerve ring surrounding isthmus. Secretory-excretory system present; excretory pore on annule 14–16; ventral gland slightly posterior to cardia.

Reproductive system diorchic, anterior testis outstretched and located to right of intestine, posterior one reflexed and located to left of intestine in holotype (position of posterior testis in paratypes could not be determined). Spicules paired, symmetrical, weakly arcuate or almost straight except for bent proximal portion; narrow, and rounded manubrium. Gubernaculum plate-like with narrow dorsal apophyses. Precloacal spine or seta absent. Thirteen or 14 pairs of subventral caudal setae, 6–8 µm long. Caudal glands not observed. Terminal cone 20–23 µm long.

Female

Similar to males, but with slightly lower ratio of a, slightly shorter cephalic setae 0.32 cbd long, shorter amphidial fovea and without caudal setae. Reproductive system didelphic, amphidelphic, with reflexed ovaries; anterior ovary to right of intestine and posterior ovary on left of intestine. Vulva a transverse slit near mid-body. Vagina straight, with thickened walls. Pars refringens vaginae not observed. Intrauterine egg not seen. Anal annule similar to adjacent annules.

Figures

Fig. 2. Ceramonema taikoraha sp. nov., ♂♂. A–C, E. Holotype (NIWA 154943). C. Paratype (NIWA 154944). A. Pharyngeal region. B. Cephalic region. C. Surface of cloacal region. D. Posterior body region. E. Posterior body region showing copulatory apparatus. Scale bar: A = 45 µm; B = 25 µm; C = 18 µm; D–E = 27 µm.

Fig. 3. Ceramonema taikoraha sp. nov., paratype, ♀ (NIWA 154944). A. Surface view of cephalic region. B. Optical section of cephalic region. C. Reproductive system. D. Posterior body region. Scale bar: A–B = 30 µm; C = 47 µm; D = 37 µm.

Fig. 4. Ceramonema taikoraha sp. nov., paratypes (NIWA 154944), light micrographs. A. ♀, surface view of anterior body region. B. ♀, optical section of anterior body region. C. ♂, surface view of cuticle. D. Entire female. Scale bar: A–C = 20 µm; D = 50 µm.