Trischistoma gracile Andrássy, 1985

Synonyms

Trischistoma macroseta Vinciguerra & La Fauci, 1978 Trefusia monodelphis Bussau, 1990

Measurements (after Andrássy, 1985)

Females: L = 1000–1200 μm; a = 49–58; b = 4.4–5.3; c = 12–14; c’ = 4.7–5.9; V = 73–78%. Male: L = 800–1100 μm; a = 41–57; b = 3.7–5.2; c = 8–13; c’ = 4–6.

Description (after Andrássy, 1985)

Cuticle very finely annulated, thin. Head rounded, 10–13 μm wide. Six outer labial setae 5–7 μm long (60% of body diameter), four cephalic setae 5–7 μm long, much thinner. Denticles minute. Amphids just behind denticles. Vulva not sclerotized; no postvulval uterine sac. Vulva–anus distance 1.7–2.1 times tail length. Spicules 25–32 μm, gubernaculum 9–12 μm long. No supplements. Tail 82–86 μm long, S-shaped, either strongly bent dorsad, or first dorsad then ventrad.

Diagnosis and Relationships

Trischistoma gracile differs from T. otaika sp. nov., T. monohystera, T. equatoriale in lack of a postvulval uterine sac and shorter body (1000–1200 μm vs 1215–1326 μm, 1500–2100 μm & 1370–1620 μm, respectively).

Females of T. gracile are similar to those of T. triregius sp. nov., T. pellucidum, T. waiotama sp. nov. and T. tukorehe sp. nov. in lacking a postvulval uterine sac. However, T. triregius sp. nov., T. pellucidum, and T. waiotama sp. nov. by have shorter bodies (611–846 μm, 680–850μm & 675–908 μm respectively vs 1000–1200 μm). It differs from T. tukorehe sp. nov. in de Man’s ratios a (49– 58 vs 39–47), b (4.4–5.3 vs 3.8–4.1) and c ’ (4.7–5.9 vs 3.9–4.9).

Trischistoma gracile also can be differentiated from T. tukorehe sp. nov. in having two prominent dorsal teeth not minute denticles.

Habitat and distribution

Aquatic, also in coastal dunes from Europe (Germany, Hungary, and Italy). Andrássy described this species from an algal mat in a small pool at Fényesfürdő (1985). Etymology

The species epithet gracilis (Latin) means: graceful or charming.