Trischistoma otaika, Zhao, Zeng Qi, 2011

Zhao, Zeng Qi, 2011, A review of the genus Trischistoma Cobb, 1913 (Nematoda: Enoplida), with descriptions of four new species from New Zealand, Zootaxa 3045, pp. 1-25 : 9-12

Trischistoma otaika sp. nov.

( Figs 5 , 6 )

Measurements

Table 2.

Material examined

Holotype: NNCNZ, slide No. 269.

Paratypes: three females. NNCNZ, slide Nos 2615–2616.

Description

General. Body slender, 26–30 μm diameter at mid-region, bent dorsad mainly in the posterior part ( Fig. 5 B). Orthometanemes present ( Fig. 6 G). Cuticle very thin, 1–2 μm thick, rough surface, two separated lines in each lateral field defined by four incisures, dorso-lateral and ventro-lateral, more or less parallel, arising at cephalic setae, ending posterior to anus by about two anal body diameters. Labial region broadly rounded, slightly offset, separated from neck, 12.5–15.0 μm wide ( Figs 5 A; 6B). Labial papillae small. Outer labial and cephalic setae in two circles, separated by 5–7 μm. Outer labial setae 4.5–5.3 μm long (one third of labial diameter), cephalic setae 3.6–4.0 μm long. Ventral cervical setae absent. Amphid small, calyciform ( Fig. 6 C).

Mouth cavity quite narrow; dorsal tooth large for the genus, 1.2–1.3 times head diameter from anterior of body, posterior tooth not seen. Oesophagus cylindrical, strongly muscular, 179–259 μm long. Dorsal pharyngeal gland opens directly into mouth cavity. Cardia small, disc-like, without glands between pharynx and intestine ( Figs 5 A; 6D). Intestine with wide lumen. Rectum about as long as anal body diameter. Coelomocytes present, circular.

Female. Gonad prodelphic, 222–233 μm long, or 17–18 % of body length, reflexed but tip not reaching vulva ( Fig. 5 C). Distance between posterior end of oesophagus and vulva 2.5–2.6 times longer than oesophagus. Vulval lips slightly sclerotized, vagina short, 28–34% of body diameter. Posterior uterine sac 113–153 μm long, about 4–5 times body diameter or more than half the distance from vulva to anus ( Figs 5 D; 6E). Uterus containing 0– 1 eggs, each 100–113 μm or 3.3–4.3 times body diameter long, and 23–25 μm in diameter. Vulva-anus distance 2.5–2.7 times tail length. Tail 81–98 μm long, 6.7–7.8% of total body length, conoid, ventrally bent with straight or dorsally curved tip. Caudal glands three, spinneret small ( Fig. 5 D).

Male. Not known.

Locality and habitat

Holotype and paratypes from soil and litter, 0–10 cm depth from natural podocarp forest ( Podocarpus spp.), Otaika , New Zealand (35º 46.851 S, 174º 16.877 E). Coll. Chris Winks, 8. iii. 2008.

Diagnosis and Relationships

Trischistoma otaika sp. nov. is characterised by having a postvulval uterine sac and a prominent dorsal tooth ( Figs 5 A; 6B & E).

Trischistoma otaika sp. nov. is differentiated from T. triregius sp. nov., T. waiotama sp. nov., T. pellucidum , T. tukorehe sp. nov. and T. gracile , which do not have a postvulval uterine sac.

Females of T. otaika sp. nov. are similar to T. monohystera and T. equatoriale in having a postvulval uterine sac. However, T. otaika differs from T. monohystera in having a short body (1215–1470 μm vs 1500–2100 μm), short tail (3–4.5 vs 5–7 anal body diameters long) and long postvulval uterine sac (more than half vulva-anus distance vs less than half vulval-anus distance). T. otaika differs from T. equatoriale in vulval position V (73–76 vs 81–82%).

Based on SSU and LSU molecular phylogenetic studies ( Figs 3 ; 4), Trischistoma otaika sp. nov. differed from Trischistoma triregius sp. nov. and T. waiotama sp. nov. by 1.57% (26 in 1657 bp), 0.48% (8 in 1657 bp), respectively for SSU; and by 10% (77 in 768 bp) and 6.5% (50 in 768 bp) respectively for LSU.

Etymology

Otaika refers to the type locality. It is used here as a noun in apposition.

Figures

FIGURE 3 Bayesian tree inferred from SSU gene rDNA sequences. Posterior probabilities exceeding 50 % are given on appropriate clades. Nematode species, GenBank numbers are listed for each taxon.

FIGURE 5 Trischistoma otaika sp. nov. female. A: Pharyngeal region, ventral, showing large big dorsal tooth. B: Entire body. C: Vulval region, lateral .. D: Tail & postvulval uterine sac. Scale bars: A, B, C, D = 50 μm.

FIGURE 6 Trischistoma otaika sp. nov. female. A: Pharyngeal region, showing cuticle in the anterior part. B: Pharyngeal region, lateral, large dorsal tooth (arrowed). C: Pharyngeal region, amphid aperture. D: Oesophago-intestinal junction (arrowed). E: Postvulval uterine sac, lateral. F: Vulva, uterus and ovary, lateral. G: Metanemes (arrowed). H: Tail, anus (arrowed), coelomocytes (arrowed).