Trischistoma ripariana, 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 : 175

Trischistoma ripariana n. sp.

Measurements. Table 1 .

Trischistoma ripariana n. sp. was collected by the second author in July 2012 from the surface litter layer along a stream bank near Oakville, Napa County, California, USA.

Female (n = 18). Body slender, curved and dorsally bent posteriorly; some specimens with the tail dorsally reflexed after fixation. Cuticle thin (1.0 m) and finely striated under SEM. Lip region rounded, 7–11 (9.5±0.23) m wide, continuous with the body contour, consisting of three lips, each with two small labial papillae at the base. Head 10–12 (11±0.2) m wide at the level of the outer labial setae (Figs. 1,2).

Body with a few scattered somatic setae close to the vulva region, cervical setae absent; anterior sensillae in three whorls, the inner whorl consisting of two small papillae at the base of each lip (inner labial papillae); the second of six outer labial setae, oriented slightly anteriorly and 4–6 (5±0.1) m long, the length almost 50% of the labial diameter. The third whorl of four cephalic setae, 4–6 (4.9±0.1) m long, are much thinner than the outer labial setae and 7–12 (10±0.3) m from the anterior end. Amphid apertures rather obscure, posterior to the cephalic setae 15–28 (20.7± 0.7) m from the anterior end. Dorsal tooth small, 13–19 (15.8±0.42) m from the anterior end; small subventral teeth 3–7 (4.1±0.85) m posterior to the dorsal tooth. Pharynx cylindrical, strongly muscular, 189–236 (213.5±2.7) µm long and 21–25 (22.4 ±0.26)% of total body length, terminating in a small cardia, 4–8 (5.7±0.2) m long and 6–12 (9.4±0.4) m wide ( Fig. 1 ).

Genital system monovarial prodelphic without a post-uterine sac, the ovary in most of the specimens is reflexed; but outstretched in one specimen. Vulva width 19 m, with small, slightly protruding lips and with small rod-like sclerotized structures. Distance between posterior of pharynx and vulva 499–660 (559±9.1) m. Vulva to anus distance 108–161 (133±2.7) m. Tail elongate conoid, 34–57 (46±1.8) µm long, occupying 2.5–5.9 (4.7±0.21)% of total body length. A pair of setae in latero-dorsal position on the tail posterior to the anus. Spinneret small, 1–4 (1.6±0.31) µm long.

Male: Unknown.

Type habitat and locality. Surface organic material and rhizosphere soil surrounding a California Bay tree on stream bank, next to Mondavi Vineyard, Oakville, California, N 38°25'50.3" W 122°25'13.2", 86 m above sea level.

Type specimens. Holotype female CNHE 9258 and paratypes CNHE 9259 of T. ripariana n. sp. are deposited in the CNHE (Coleccion Nacional de Helmintos, Instituto de Biologia, Universidad Nacional Autónoma de México); paratypes A-079- 2 in CNCP (Colección Nematologica del Colegio de Postgraduados, Texcoco, México, UCRNC (Nematode Collection of the University of California, Riverside), and USDANC USDA Nematode Collection, Nematology Investigations, Beltville, MD, USA).

Etymology. The specific epithet is derived from the Latin riparius, referring to the stream bank locality of the type habitat.

Diagnosis and relationships. Trischistoma ripariana n. sp. is characterized by its small, very thin, body 0.8–1.0 (0.95±0.01) mm; thin cuticle, small index c, 17–29 (21±1.3) and short tail, 34–57 (46.2±1.8) µm which is 2.5–5.9 (4.7±0.21)% of body length.

Trischistoma ripariana n. sp. is similar at T. pellucidum Cobb, 1913 in the index b and in the position of the vulva; it can be distinguished by the body length, 0.8–1.1 vs. 0.6–0.8 mm, by the short tail 34–57 (46.2±1.8) vs. 50–60 µm long, the indices a = 45–59 vs. 36–43 and c = 17–29 vs. 13–14. It resembles T. waiotoma Zhao, 2011 , in the index b and in the position of vulva, but it can be distinguished by the length of the tail 34–57(46±1.8) vs 50–64, in the indices a and c, 45–59 and 17–29 vs 32–41 and 10.9–15.6, respectively.

Molecular characteristics. Trischistoma ripariana was distinct in nucleotide sequence when compared to other Trischistoma congeners. Trischistoma ripariana showed 15 or more differences in pairwise congeneric comparisons.

Figures

FIGURE 1. Trischistoma ripariana n. sp. Female A – F. A: Anterior half body; B: Anterior end; C: Posterior end body; D: Pharyngeo-intestinal junction; E, F: Tails.