Genus Trischistoma Cobb, 1913

Diagnosis (from Zullini 2006, Andrássy 2007 and Zhao 2011)

Trischistomatidae . Body length 0.6–2.2 mm. Very slender, posterior portion often bent dorsally. Cuticle smooth, thin, not annulated. Six longer outer labial setae and four shorter, thinner cephalic setae in two separate circles. Pharynx strongly muscular. Buccal cavity with minute denticles. Female monodelphic with anterior reflexed ovary, with or without post-vulval uterine sac; vulva located at 67–83% of body length from anterior extremity. Tail bent dorsally, 3–7 times as long as cloacal/anal body diameter, usually more or less S-shaped. Males rare; reproductive system monorchic with single reflexed testis. Spicules not surrounded by muscular pouch. Spermatozoa ellipse-shaped or fusiform, sometimes unusually large, up to 1 cbd long. No or few (1–3) papillose precloacal supplements. Tail conical. Seventeen species.

Type species

Trischistoma pellucidum Cobb, 1913 . = Tripyla pellucida – Micoletzky, 1922.

Other valid species

T. abharensis Asghari, Eskandari, Maafi, Zhao, Alvarez-Ortega & Nadirkhanloo, 2015 .

T. corticulensis Cid del Prado-Vera, Ferris & Nadler, 2016.

T. equatoriale Andrássy, 2006 .

T. gracile Andrássy, 1985 .

= Trefusia monodelphis Bussau, 1990 .

T. helicoformis Cid del Prado-Vera, Ferris & Nadler, 2016.

T. minor Tahseen & Nusrat, 2010 .

T. monohystera (de Man, 1880) Schuurmans Stekhoven, 1951 .

= Tripyla monohystera de Man, 1880 .

= Tripylina monohystera (de Man, 1880) .

= Tripylina monohysteroides Altherr, 1963 .

T. otaika Zhao, 2011 .

T. ripariana Cid del Prado-Vera, Ferris & Nadler, 2016.

T. subtilissimum Andrássy, 2011 .

T. taiguensis Xu, Zhao & Wang, 2015 .

T. tenuissimum Andrássy, 2011 .

T. riregius Zhao, 2011 .

T. ukorehe Zhao, 2011 .

T. veracruzense Cid del Prado-Vera, Ferris & Nadler, 2010.

T. waiotama Zhao, 2011 .

Species inquirenda

T. conicaudatum Schuurmans Stekhoven, 1951 .

Remarks

Trischistoma was revised by Zhao (2011). Asghari et al. (2015) provided a table with morphometrics of all Trischistoma species, and Cid del Prado-Vera et al. (2016) provided a key to the species of the genus. Trefusia monodelphis Bussau, 1990 was synonymised with Trischistoma gracile by Andrássy (2007).