Trefusialaimus idrisi Leduc, 2013

Leduc, Daniel, Zhao, Zeng Qi & Sinniger, Frederic, 2020, Halanonchus scintillatulus sp. nov. from New Zealand and a review of the suborder Trefusiina (Nematoda: Enoplida), European Journal of Taxonomy 661 (661), pp. 1-45 : 19

Trefusialaimus idrisi Leduc, 2013

Table 1 ; Figs 3–4

Material examined

NEW ZEALAND • 2 ♀♀; western Chatham Rise off the east coast of New Zealand’s South Island, Tangaroa voyage TAN0705 , station 157, surface (0–5 cm) sandy silt sediments; 42.785º S, 176.715º W; depth 1029 m; 16 Apr. 2007; D. Leduc leg.; NIWA 139242 . • 1 ♀; same collection data as for preceding; NNCNZ 3330 .

Description

Female

Body cylindrical, slender, tapering slightly towards anterior extremity, with slight golden colouration due to the presence of numerous round, ca 1 μm diameter, golden inclusions. Cuticle smooth. Cephalic region rounded, slightly set off from body due to thickened cuticle and constriction immediately posterior to cephalic setae. Three lips, each bearing two small, conical inner labial papillae. Six outer labial setae and four cephalic setae in one circle, all with single joint; cephalic setae slightly longer than outer labial setae (6–9 vs 7–10 μm). Sub-cephalic and somatic setae absent. Amphid pocket-shaped with transverse aperture, ca 6–9 μm wide by 2 μm high. Buccal cavity funnel-shaped, without teeth. Pharynx cylindrical, slightly wider posteriorly, completely surrounding buccal cavity. Nerve ring situated at 49– 66% of pharynx length. Secretory-excretory system not observed. Cardia small, surrounded by intestine. Numerous sperm cells are present throughout the pseudocoelom between pharynx and anus, as well as in the uterus. Reproductive system with two opposed and outstretched ovaries, both to the right or left of intestine. Vagina at about two thirds of body length from anterior. Tail long, ca 8–10% of total body length, narrow, gradually tapering, without setae; spinneret not observed.

Remarks

The female specimens described here agree well with the male specimen described from the central Chatham Rise (350 m depth) in the arrangement of anterior sensilla, size and position of the amphids, presence of numerous golden inclusions and tail shape. The female specimens, however, were characterized by longer bodies (5004–5947 vs 4539 μm) and shorter tails (cʹ = 18–21 vs 38).

This is the first time that female Trefusialaimus specimens are described. The structure of the female reproductive system in this species, which consists of two opposed and outstretched ovaries, is unusual for the Enoplida , although it has been observed in Cytolaimium exile (Trefusiidae) , and Mediolaimus Tahseen, Sultana, Khan & Hussain, 2012 and Rogerus Hoeppli & Chu, 1934 ( Enoplida , family Rhabdolaimidae Chitwood, 1951 ). It is unclear how sperm had entered the pseudocoelom of the female specimens we observed; however, the same observation was made previously for a juvenile of the same species ( Leduc 2013).

Figures

Fig. 3. Trefusialaimus idrisi Leduc, 2013, ♀ (NIWA139242). A. Anterior body region. B. Cephalic region. C. Posterior body region. D. Reproductive system. Scale bars: A = 50 μm; B = 20 μm; C = 90 μm; D = 125 μm.

Figure 4. Trefusialaimus idrisi Leduc, 2013, ♀ (NIWA139242), light micrographs. A. Optical crosssection of cephalic region showing buccal cavity, lips and pharynx. B. Surface view of cephalic region showing outer labial setae and amphid. C. Mid-body region showing intestine and sperm cells in pseudocoelom (arrows). Scale bars: A–B = 15 μm; C = 22 μm.