Trischistoma triregius, 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 : 4-8

Trischistoma triregius sp. nov.

( Figs 1 , 2 )

Measurements

Table 2.

Material examined

Holotype: National Nematode Collection New Zealand ( NNCNZ), slide No. 268. Paratypes: twelve females and two juveniles. NNCNZ, slide Nos 2599–2611 (2599–2608 were measured).

Description

General. Body slender, 20–27 μm diameter at mid-region, bent dorsad mainly in the posterior part ( Fig. 1 A). Orthometanemes present, frontal and caudal filament obscure. Cuticle very thin, 0.5–1.5 μm thick, rough surface, two separated irregular lines in each lateral field defined by 4 incisures, beginning at the level of cephalic setae merging at about 2 times body diameter anterior to nerve ring and separating again at about 1.5–2 times body diameter posterior to nerve ring before reaching to region of caudal glands ( Fig. 2 B). Labial region broadly rounded, not offset, 10–12 μm wide ( Figs 1 A; 2A). Inner labial papillae small. Outer labial and cephalic setae in two circles separated by nearly the length of a cephalic seta (5–7 μm) ( Figs 1 B; 2C). Six outer labial setae 5–6 μm long (about half as long as labial diameter), cephalic setae 3–5 μm long. A pair of very thin sublateral cervical setae ( Fig. 1 B) 85–96 μm from anterior end, or 44–52% of oesophagus length. Amphid small, calyciform.

Mouth cavity narrow; two minute dorsal teeth, anterior 1–1.4 times head diameter from anterior end, and posterior 2–2.5 times head diameter from anterior end. Oesophagus cylindrical, strongly muscular, 156–219 μm long. Dorsal pharyngeal gland opening directly into mouth cavity. Cardia small, disc-like. No glands between pharynx and intestine ( Figs 1 C; 2D). Intestine with wide lumen. Rectum about as long as anal body diameter. Coelomocytes present, circle shaped.

Female. Gonad prodelphic 130–211 μm long or 13–25% of body length, reflexed, but tip not reaching vulva ( Figs 1 D; 2E). Distance between posterior end of oesophagus and vulva 1.8–2.7 times longer than oesophagus. Vulval lips slightly sclerotized, vagina short, one third of body diameter. Posterior uterine sac absent. Uterus with 0– 2 eggs, each 69–81 or 2.6–3.6 body diameter long and 13–19 μm in diameter. Vulva–anus distance 1.5–2.0 tail lengths. Tail 44–72 μm long, 6.3–8.5% of total body length, conoid, ventrally bent with straight or dorsally curved tip. Caudal glands three, spinneret small ( Fig. 1 E).

Male. Not known.

Locality and habitat

Holotype and paratypes from 0–10 cm topsoil and litter mixture, Three Kings Islands, New Zealand (34º 09.778 S, 172º 08.544 E). Coll. Richard Leschen, 7. xi. 2007.

Diagnosis and Relationships

Trischistoma triregius sp. nov. is characterised by having a pair of lateral cervical setae, and short body ( Fig. 1 B).

The genus Trischistoma contains two groups of species, one with females having a post-uterine sac, and one without ( Table 3). Trischistoma triregius sp. nov. belongs to the latter group, with T. waiotama sp. nov., T. pellucidum Cobb, 1913 , T. tukorehe sp. nov. and T. gracile Andrássy, 1985 .

TABLE 2. Morphometric data (length in µm) for Trischistoma triregius sp. nov., T. otaika sp. nov., T. waiotama sp. nov., and T. tukorehe sp. nov.

Holotype female Paratype females

Mean ± S.D. (range)

T. T. triregius T.otaika T. T. waiotama T. triregius T. otaika T. tukorehe

waiotama sp. nov. tukorehe sp. nov. sp. nov. sp. nov. sp. nov.

sp. nov. sp. nov. sp. nov.

( Waiotama ) (Botanical

Garden)

n 1 1 1 1 5 10 11 3 10 a 36.9 30.4 51.6 36.7 35.8 ± 2.0 36.1 ± 2.4 33.0 ± 3.8 46.2 ± 2.1 42.2 ± 2.6

(32.4–37.3) (32.8–41.3) (29.8–37.0) (43.7–48.8) (38.5–47.1) b 4.5 4.5 5.3 3.8 4.2 ± 0.2 4.6 ± 0.2 4.2 ± 0.3 4.7 ± 0.1 4.0 ± 0.1

(4.0–4.5) (4.4–5.1) (3.7–4.6) (4.7–4.8) (3.8–4.1) c 13.8 14.8 13.8 10.7 14.2 ± 1.0 12.7 ± 1.4 13.6 ± 1.4 14.0 ± 0.9 12.7 ± 1.0

(13.3–15.6) (10.9–14.4) (11.7–15.9) (12.8–15.0) (11.4–14.8) c’ 4.0 3.2 4.8 4.7 3.7 ± 0.3 3.9 ± 0.4 3.4 ± 1.3 4.4 ± 0.1 4.6 ± 0.3

(3.4–4.1) (3.5–4.5) (3.0–4.7) (4.2–4.6) (3.9–4.9) V 81.6 81.0 73.1 75.8 81.9 ± 0.9 80.1 ± 1.3 79.3 ± 2.9 75.7 ± 0.1 73.9 ± 1.2

(80.9–83.1) (79.3–81.8) (73.2–82.3) (75.6–75.7) (72.3–75.6) Body 879 763 1470 1015 795.7 ± 74.6 772 ± 78.7 716 ± 80.5 1264 ± 46.2 1092 ± 56.1 length (675–863) (681–908) (611–846) (1215–1326) (1088–1149) Pharynx 194 170 275 265 186.7 ± 10.4 167.3 ± 12.8 171.9 ± 23.5 266.2 ± 9.3 270.1 ± 10.5 length (171–198) (151–187) (137–219) (259–279) (251–287) Vulva– 718 619 1074 769 651.9 ± 63.4 619.2 ± 67.6 571.6 ± 61.7 961.6 ± 42.8 807.4 ± 41.4 anterior (546–708) (532–743) (479–678) (919–1004) (730–853) Females of T. triregius sp. nov. are similar in total body length to T. waiotama sp. nov. and T. pellucidum , but are shorter than other known species, T. otaika sp. nov., T. tukorehe sp. nov., T. gracile , T. equatoriale Andrássy, 2006 and T. monohystera (de Man, 1880) Schuurmans Stekoven, 1951 ( Table 3).

Trischistoma triregius sp. nov., with a pair of sublateral cervical setae, differs from T. waiotama sp. nov. which has ventral seta in the cervical region, and differs from T. pellucidum which lacks setae in the cervical region ( Table 3).

Based on the SSU and LSU molecular phylogenetic studies ( Figs 3 ; 4), Trischistoma triregius sp. nov. differed from T. otaika sp. nov. and T. waiotama sp. nov. by 1.57% (26 in 1657 bp), 1.51% (25 in 1657 bp), respectively for SSU; and by 10% (77 in 768 bp) and 8.1% (62 in 768 bp) respectively for LSU.

Etymology

The name triregius alludes to the Three Kings Islands.

Cervical

Species L (µm) a b c c’ V % References

seta or setae Females

716 33 4.2 13.6 3.4 79.3

triregius 1 pair This paper (611–846) (29.8–37.0) (3.7–4.6) (11.7–15.9) (3.0–4.7) (73–82)

1264 46 4.7 14.0 4.4 75.7

otaika no This paper (1215–1326) (43.7–48.8) (4.7–4.8) (12.8–15.0) (4.2–4.6) (73–76)

780 36 4.5 13.2 3.8 80.7

waiotama 1 single This paper (675–908) (32–41) (4.0–5.1) (10.9–15.6) (3.4–4.5) (79–83)

1092 42 4.0 12.7 4.6 73.9

tukorehe no This paper (1088–1149) (38.5–47.1) (3.8–4.1) (11.4–14.8) (3.9–4.9) (72–76)

equatoriale (1370–1620) (38–44) (4.9–5.8) (15.2–20.6) (3.2–3.8) (81–83) unknown Andrássy 2006

gracile (1000–1200) (49–58) (4.4–5.3) (12–14) (4.7–5.9) (73–78) unknown Andrássy 1985 de Man 1880;

monohystera (1500–2100) (45–75) (4.5–6.5) (10–17) (5–7) (74–82) unknown Schuurmans Stekhoven

1951 750 39 4.5 13.2?76

pellucidum no Andrássy 1968 (680–850) (36–43) (4.4–4.6) (13–14) (73–74)

Males

equatoriale (1500–1740) (46–48) (5.4–5.6) (14.4–19.3) (3.2–4.2) no Andrássy 2006

gracile (800–1100) (41–57) (3.7–5.2) (8.0–13.4) (4–6) no Andrássy 1985 de Man 1880;

monohystera (1500–2200) (64–94) (5.7–7.2) (10–14) (5–7) no Schuurmans Stekhoven

1951

Figures

FIGURE 1 Trischistoma triregius sp. nov. female. A: Entire body, lateral. B: Pharyngeal region, ventral, showing pair of cervical seta. C: Pharyngo-intestinal junction region, lateral. D: Genital region, lateral. E: Tail, lateral. Scale bars: A, B, C, D, E = 50 μm.

FIGURE 2 Trischistoma triregius sp. nov. female. A: Pharyngeal region, lateral. B: Pharyngeal region, lateral, showing cuticle in anterior part. Arrows indicate lines in cuticle. C: Pharyngeal region, ventral, showing outer labial and cephalic setae (arrowed) in two separate circles. D: Oesophagus and intestine junction (arrowed). E: Genital region, lateral. F Vulva opening. G. Vagina. H: Coelomocyte (arrowed).

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.