Trischistoma pellucidum Cobb, 1913

Xu, Yu Mei, Zhao, Zeng Qi & Wang, Jian Ming, 2015, A new species and a new record of Trischistoma Cobb, 1913 (Nematoda: Enoplida: Trischistomatidae) from Shanxi Province, China, Zootaxa 3937 (3), pp. 564-576 : 571-574

Re-description of Trischistoma pellucidum Cobb, 1913 .

(Figs 6A–E & 7A–G)

Measurements. Table 3 .

Description. Female (n=17). Body dorsally bent when fixed, posterior region more curved than anterior (Fig. 6A). Cuticle smooth, cuticular thickness 1–1.5 µm.

Head rounded, continuous with body contour, 8–12 µm diameter, head height 1–3 µm. Inner labial papilla distinct (Fig. 7A). Six long labial and four short cephalic setae in two separate whorls (Figs 6B & 6C); six longer labial setae 5–8 µm long or 46–79% of head diameter, four shorter cephalic setae 2.5–5 µm or 25–50% of head diameter, thinner than the longer labial setae. Distance between labial setae and cephalic setae 5–8 µm. One conspicuous dorsal tooth, 1.2–1.6 times head diameter from anterior end, subventral denticles indiscernible (Figs 6B, 7B). Amphid small, calyciform, 1.0–2.5 times lip diameter from anterior end, amphidial apertures 2–3 µm wide (Figs 6B, 7C). Excretory pore not seen. Nerve ring 68–76 µm or 40–44% of pharyngeal length from anterior end of body (Fig. 7C). Pharynx 147–177 µm long, occupying 20–25% of the body length. Cardia between pharynx and intestine inconspicuous (Figs 6C, 7E).

Gonad prodelphic, 90–160 µm long, or 13–22% of body length, reflexed but tip not reaching vulva (Fig. 7D). Vulva a small transverse slit, flush with body contour, no sclerotized structures, vagina short, 2–6 µm long, 10–29% of body diameter (Figs 6D & 7D). No post-vulval uterine sac. Vulva to anus distance 71–180 µm long, or 1.8–3.9 times tail length. Tail length 37–59 µm, occupying 5.0–8.0% of total body length, bent dorsally (Figs 6E, 7F). Three tandem caudal glands and a small terminal spinneret are present on the tail (Figs 7F, 7G).

Male. Not found.

When SSU sequences of the Chinese isolate of T. pellucidum are compared with the molecular data for the most closely related species ( T. otaika from New Zealand), there are 1% (15 in 1585 bps including 1 gap) differences between the two species. When LSU sequences are compared with the most closely related species ( T. triregius from New Zealand), there are 6% (44 in 753 bps including 2 gaps) differences between the two species. Unfortunately, there is no molecular data of T. pellucidum available from earlier collections.

Habitat and locality. Trischistoma pellucidum Lv 09 samples (including 7 females and 5 juveniles) collected from soil and litter mixture, 0–10 cm depth under a cypress tree, Pangquangou National Reserve, Lvliang city, Shanxi province (111°27'55" E, 37°51'12" N) in July 2013, by Li Fang Yin; JC05 samples (including 19 females and 2 juveniles) were from soil and litter mixture, 0–10cm depth under a pine tree, Yangcheng county, Jincheng city, Shanxi province (112°20'57" E, 35°20'12" N) in August 2013 by Yun Long Jiu.

Remarks. Trischistoma pellucidum has been reported from Mexico, Jamaica, Paraguay, India and Spain (morphometrics listed in Table 3 ) ( Andrássy 1985; Tahseen & Nusrat 2010; Lluch 1996). The nematode collected from China agrees well in all aspects with T. pellucidum Cobb, 1913 . However, some minor differences were observed with the description of Andrássy, 1968. The Chinese nematode tends to have a greater V value (70–83% vs 73–74%) and shorter tail length (37–60 vs 50–60 µm).

FIGURE. 6. Trischistoma pellucidum female. A: Entire body. B, C: Anterior body region, lateral view, showing outer labial setae, cephalic setae, dorsal tooth and amphid. D: Genital region. E: Tail. Scale bars: A=50 Μm, B, C, D, E=20 Μm.

FIGURE. 7. Trischistoma pellucidum photomicrographs. A: Anterior region, inner papillae shown. B: Pharyngeal region, lateral view; dorsal tooth arrowed. C: Pharyngeal region, lateral view; amphid aperture and nerve ring arrowed. D. Genital region; vulva arrowed. E: Pharynx and intestine junction (arrowed). F: Tail region, caudal glands arrowed. G: Spinneret.

Tables

TABLE 3. Morphometric data of Trischistoma pellucidum from China and some published records from elsewhere (mean ± S. D, with ranges). Measurements are in micometers.

Lvliang city character (this paper China) (n=6)	Jincheng city (China) (n=11)	Jamaica (Cobb 1913)	Mexico, Paraguay (Andrássy 1968; Tsalolikhin 1983)	Spain (Lluch 1996)	India (Tahseen & Nusrat 2010)
725 ± 65 L (613–795)	785 ± 30 (723–819)	600	680–850	617–815	641–748
36.5 ± 2.4 a (31.7–39.5)	36.3 ± 2.5 (33.0–40.5)	38	36–43	17.0–32.5	35.7–43.5
4.6 ± 0.3 b (4.0–5.0)	4.7 ± 0.1 (4.5–5.0)	4.6	4.4–4.6	3.9–4.3	4.3–5.2
16.6 ± 2.2 c (13.4–19.7)	14.9 ± 1.1 (13.3–16.8)	12.5	13–14	10.6–13.0	10.3–14.5
3.3 ± 0.5 c' (2.9–4.5)	3.6 ± 0.4 (3.0–4.1)	3.8	N/A	3.4–4.1	4.1–5.8
75.2 ± 5.4 V (70.2–83.2)	72.8 ± 3.1 (70.7–81.4)	80	73–76	76.8–84.6	76.4–83.6
10.2 ± 1.5 Head diameter (7.7–12.1)	11.2 ± 1.0 (9.4–12.6)	N	12–14	N/A	9–11
19.9 ±1.5 Body diameter (16.9–21.1)	21.7 ±1.8 (18.5–23.5)	15.6	18	N/A	17–19
158.4 ± 8.3 Pharynx length (147–171)	168.6 ± 6.5 (160–177)	132	155	N/A	125–166
Nerve ring- 66.7 ± 4.8 anterior end (61.1–73.5)	72.2 ± 2.5 (67.6–75.5)	54.6	N/A	N/A	50–63
44.4 ± 7.8 Tail length (36.7–58.3)	52.8 ± 4.5 (44.6–58.9)	48	53	N/A	50–70
Anal body 13.3 ± 1.3 diameter (11.6–15.2)	14.6 ± 1.8 (11.2–18.2)	12.6	N/A	N/A	11–13
9.0 ± 1.6 Rectum length (6.4–11.7)	12.4 ± 1.3 (9.5–13.8)	N/A	N/A	N/A	7–12
Vulva-anus 138.4 ± 42.3 distance (70.8–180.6)	161.0 ± 25.8 (89.6–179.4)	72	N/A	N/A	70–100
N/A: data not available in the original paper