Trischistoma corticulensis, Prado-Vera, Ignacio Cid Del, Ferris, Howard & Nadler, Steven A., 2016

Prado-Vera, Ignacio Cid Del, Ferris, Howard & Nadler, Steven A., 2016, Five new species of the family Trischistomatidae (Nematoda: Enoplida) from North and Central America, with keys to the species of Trischistoma and Tripylina, Zootaxa 4109 (2), pp. 173-197 : 178-180

Trischistoma corticulensis n. sp.

Measurements. Table 1 .

Trischistoma corticulensis n. sp. was collected by the first author from moss on tree bark in an ecological reserve at the La Mancha Ecological Institute, Veracruz, México in August 2012.

Female (n= 10). Body slender, curved, bent dorsally at the posterior end, tail dorsally reflexed after fixation. Cuticle finely striated under SEM and thin, 1.0 m; lip region continuous with body contour, rounded and asymmetric, 7–12 (9.0±0.47) m wide and 10–14 (13±0.4) m at the level of the cephalic setae. There are a few somatic setae and one cervical seta. (Figs. 3,4).

Mouth with three lips, opening somewhat dorsally shifted, mouth cavity narrow, encircled by pharyngeal musculature. Cephalic sensillae in three whorls, the inner labial setae are very small and raised slightly above the cuticular surface at the base of each lip; the six outer labial setae are oriented slight anteriorly and 4–6 (5±0.25) m long, almost 50% of labial diameter; the four cephalic setae are 3.0 (3.0±0.0) m long, much thinner than outer labial setae and 10–12 (11±0.3) m from the anterior end. Amphid apertures posterior to cephalic setae, 15–27 (21± 1.0) m from the anterior end. One cervical seta present at 29 m from the anterior end, detected only by SEM (Figs. 3,4).

Dorsal tooth very small 9–12 (10.6±0.37) m from the anterior end and subventral teeth 8–11 (9.4±0.4) m posterior to the dorsal tooth. Pharynx cylindrical, strongly muscular, 151–217 (181±6.2) µm long and 14.5–20.5 (17.6 ±0.48)% of the total body length, terminating in a small cardia, 3–10 (5.5±0.58) m long and 6–13 (9.4±0.69) m wide. Genital system monovarial prodelphic without a post-uterine sac; the ovary in most specimens is outstretched. An egg, 88 x 18 m, was observed in only one specimen. Distance between posterior end of pharynx base and vulva 396–698 (564±26.3) m. Vulva with lips protruding and without sclerotised structures. Vulva to anus distance 194–286 (247±8.9) m. Tail elongate conoid, regularly tapering, dorsally bent in some specimens, 51–84 (65±2.9) µm long and 5.1–7.2 (6.3±0.21)% of total body length. A pair of setae in latero-dorsal position on the tail posterior to the anus. Rectum length almost equal to anal body diameter. Spinneret small, 1.0 µm long (Figs. 3,4).

Male: Unknown.

Type habitat and locality. Green moss growing on bark of tropical tree at the La Mancha Ecological Institute, Municipio de Actopan, Veracruz State, México, N 19°35'49.6" W 96°22'43.3", 24 m above sea level.

Type specimens. Holotype female CNHE 9256 and paratypes CNHE 9257 of T. corticulensis are deposited in CNHE; paratypes in CNCP (A-080-2) and UCRNC and USDANC.

Etymology. The specific epithet is derived from the Spanish word for bark: corteza.

Diagnosis and relationships. The new species is characterized by the very thin and short body 0.8–1.18 (1.0±0.04) mm; thin cuticle, the index c’ = 2.8–4.4 (3.7±0.1), the position of vulva 67–73%, the relative length of the pharynx, 14.5–20.5 (17.6±0.48)% of body length, and the presence of one cervical seta.

Trischistoma corticulensis n. sp. is close to T. ripariana n. sp. in the size of the body, outer labial setae and the thin cuticle. It can be readily distinguished by the indices a = 34–45 (42±0.95) vs. 45–59 (51±0.95), c = 14–20 (16±0.56) vs. 17–29 (21±1.3), in the position of vulva 67–73 (69.6±0.5)% vs. 79–83 (81±0.2)%, in the length of the tail, 51–84 (65±2.9) vs. 34–57 (46±1.8) m and the distance vulva-anus 194–286 (247±8.9) vs. 108–161 (133±2.8). It resembles T. otaika Zhao, 2011 , in the length of the body and in the indices a and b, but it can be distinguished by the vulva position, 67–73 (69.6±0.5)% vs. 79–83%, and the length of the tail, 51–84 (65±2.9) vs. 81– 98 m.

Molecular characteristics. Trischistoma corticulensis was distinct in nucleotide sequence when compared to other Trischistoma congeners. The new species exhibited five or more nucleotide differences in pairwise congeneric comparisons.