Trischistoma monohystera

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 : 20

Trischistoma monohystera (de Man, 1880) Schuurmans Stekoven, 1951

Synonyms

Tripyla monohystera de Man, 1880. Trischistoma monhysteroides Altherr, 1963 .

Measurements (after Schuurmans Stekhoven, 1951)

Females: L = 1500–2100 μm; a = 44–75; b = 4.5–6.5; c = 10–17; c’ = 5–7; V = 74–82%. Males: L = 1500–2200 μm; a = 64–94; b = 6.4–7.2; c = 10–14; c’ = 5–7.

Description (after Schuurmans Stekhoven, 1951)

Body very slender. Cuticle smooth. Head 20 μm wide. Six outer labial setae, each 8–10 μm long (three quarters of head diameter) and four short cephalic setae 5–7 μm long. Teeth minute. Gonad prodelphic with posterior uterine sac occupying nearly half of vulva-anus distance. Eggs 90–150 × 20–30 μm. Vulva–anus distance 1.5–2 times tail length. Spicules crescentic, 30–37 μm long, gubernaculum thin. Three small supplements. Tail elongate-conoid, dorsally bent, in females 120–160 μm long.

Diagnosis and Relationships

T. monohystera is distinguished by: a long, very slender body; a moderately long postvulval sac; three supplements; and a fairly-long, slightly-bent tail.

Trischistoma monohystera can be differentiated from T. triregius sp. nov., T. waiotama sp. nov., T. pellucidum , T. tukorehe sp. nov. and T. gracile in having a postvulval uterine sac and long body.

T. monohystera is similar to T. otaika sp. nov. and T. equatoriale in having a postvulval uterine sac. However, it differs from T. otaika sp. nov. in having a long body (1500–2100 μm vs 1215–1326 μm), a long tail (morphometric index c' 5–7 vs 3–4.5) and a short postvulval uterine sac (less than half the vulva-anus distance long vs more than half the vulva-anus distance). It differs from T. equatoriale in body length (1500–2100 μm vs 1370–1620 μm), de Man’s ratios a (45–75 vs 38–44) and c ’ (5–7 vs 3.2–3.8).

Based on SSU and LSU molecular phylogenetic studies, T. monohysterra is different from T. triregius sp. nov., T. waiotama sp. nov. and T. otaika sp. nov. ( Figs 2 ; 3).

Habitat and distribution

Trischistoma monohystera is common in soil, lakes, rivers and subterranean water, occurring on every continent except Australia and Antarctica: Europe ( Netherlands, Germany, Switzerland, Denmark, Sweden, Slovakia, Hungary, Serbia, Spain, France, Italy, Lithuania, Modova, Russia), Asia ( Uzbekistan, Sumatra, China), Africa ( Egypt, Zaire), North America ( United States, Mexico, Costa Rica, Jamaica), South America ( Argentina) and New Zealand.

Etymology

The species epithet is derived from the Greek monos (μόυ⁰ς) = one, a single, and hystera (ύστέρα) = the uterus or gonad.

Remarks

Trischistoma monohysteroides Altherr, 1963 does not differ in any morphological characters from T. monohystera , therefore, in agreement with Zullini (2006), Andrassy (2007) considered it a junior synonym of the latter. The description of Tripyla monohystera longicauda Rahm, 1928 was very short and not illustrated. Therefore, its status is uncertain.

Figures

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).