Tripylella australis Xu, Zhao, Davies & Wang, 2017, sp. nov.

Description of Tripylella australis sp. nov.

(Figs 1 & 2)

Measurements. Table 1.

Female. (n = 3). Body ventrally arcuate when fixed, posterior part more curved than anterior. Cuticle very thin, 1.2–1.3 (1.2 ± 0.1) µm thick at head region, 2 (1.9 ± 0.1) µm thick at vulva region, and 1.3–1.5 (1.4 ± 0.1) µm thick at anus region. Cuticular annulation 2.0 µm wide. Body pores not apparent when examined with light microscopes. Maximum body diameter 43–44 (44 ± 0.2) µm at level of vulva. Head region rounded, smooth, slightly flat, continuous with body contour, but narrower than adjacent posterior body, 21–22 (22 ± 0.1) µm wide, 3–4 (3.6 ± 0.6) µm height (Fig. 2 B). Inner labial papillae distinct, conical, outwardly directed. Six outer labial setae and four cephalic setae arranged in one circle (Fig. 2 A). Outer labial setae conoid, 13.6–14.0 (13.9 ± 0.1) µm long or 63–65 (64 ± 1.0) % of head diameter, more or less arcuate and directed anteriorly; four short cephalic setae, 4 (4.0 ± 0.4) µm long or 17–21 (19 ± 2.2) % of head diameter, thinner than outer labial setae. Dorsal tooth and subventral teeth situated in a single small oval stomatal chamber. Dorsal tooth small, triangular, at 18–20 (19 ± 1.0) µm from anterior end. Two tiny subventral teeth situated 3–4 (3.5 ± 0.4) µm anterior to dorsal tooth. Amphid caliciform with transverse oval opening, 5 (5 ±0.1) µm wide, located 20–22 (21 ± 1.5) µm from anterior end (Figs 1 C, 2B & 2C). Excretory pore not observed in the samples. Nerve ring 103–106 (105 ± 2.0) µm from anterior end or 25–27 (26 ± 0.7) % of the pharyngeal length (Fig 1 A). Pharynx cylindrical and muscular, 384–433 (408 ± 34) µm long. Cardia conspicuous, 21–26 (23 ± 3.6) µm long and 17–20 (18 ± 2.1) µm wide (Figs 1 D & 2D). Female genital system amphidelphic, short, lacking spermatheca, gonads lying ventro-lateral to intestine, outstretched, with few oocytes, the anterior branch 162–311 (237 ± 105) µm long, or 9–17 (13 ± 4.2) % of body length, the posterior branch 208–260 (234 ± 37) µm long, or 11–14 (13 ± 1.7) % of body length (Fig. 1 E). Egg ovoid, 68 µm long and 37 µm wide, observed in reproductive system (one sample). Vulva simple, lips flat (Fig. 2 F). Vagina occupying 24–28 (26 ± 2.1) % of corresponding body diameter. No distinct prerectum. Rectum 23–29 (26 ± 4.0) µm long. Tail ventrally arcuate, tapering uniformly, and spinneret 2 (2.1 ± 0.1) µm long (Fig. 2 I). Three caudal glands arranged in tandem. Four dorsal caudal setae on tail (Figs 1 F & 2H).

Male. (n = 2). Body ventrally arcuate when fixed, posterior part more curved than anterior. Cuticle very thin, 1.7 µm thick at head region and 2.7 µm thick at anus region. Cuticular annulation 2.1–2.8 µm wide. Body pores not observed when examined with light microscopes. Maximum body diameter 37 µm at mid region of the body. Head region rounded, smooth, slightly flat, continuous with body contour, but narrower than adjacent posterior body, 22– 25 µm wide, 4 µm high (Fig. 2 E). Inner labial papillae distinct. Six outer labial setae and four cephalic setae arranged in one circle. Six outer labial setae conoid, 14 µm long or 55 % of head diameter, more or less arcuate and directed anteriorly; four short cephalic setae, 5 µm long or 20 % of head diameter, thinner than outer labial setae (only one available specimen measured for outer labial and cephalic setae). Dorsal tooth and subventral teeth situated in one single, oval, stomatal chamber. Dorsal tooth small, triangular, at 24–27 µm from anterior end (Fig. 2 E). Two tiny subventral teeth situated 4 µm anterior to dorsal tooth. Amphid caliciform with transverse oval opening, 4–5 µm wide, located 17–22 µm from anterior end. Excretory pore not seen in the samples. Nerve ring 100–111 µm from anterior end or 25–27 % of the pharyngeal length. Cardia conspicuous, 22–24 µm long and 14– 18 µm wide. Ventromedian supplementary papillae 15, extending from cloaca to near anterior body end, with 6 to 7 present in the pharyngeal region. Testis outstretched, developing germ cells in one column (Fig. 2 G). Spicule hornshaped, ventrally arcuate, 36–38 µm long along mid-line. Gubernaculum straight, 15–16 µm long (Fig. 2 J). Tail curved ventrally, ending in a terminal spinneret, 3–4 µm long. Three caudal glands arranged in tandem, posterior to the cloaca. Four dorsal caudal setae on tail (Fig. 2 K).

Type locality and habitat. Holotype and paratypes collected from soil of Glenbog State Forest, Bega Valley, New South Wales, Australia (36.70000076° S, 149.4833069° E; altitude ca 1000 m). Coll. J.A. Simpson, 24.vii.1985.

Material examined. Holotype, female, collected from soil of Glenbog State Forest, Bega Valley, New South Wales, Australia. It is deposited in the Australian National Nematode Collection (ANNC) (slide no. 164), CSIRO Canberra. Paratypes are in the Waite Insect and Nematode Collection (WINC), The University of Adelaide, Adelaide, South Australia; 2 females, slide WINC nos. 017619–017620 and 2 males slide WINC no. 0 17633.

Diagnosis and relationships. Tripylella australis sp. nov. is characterized by having females with a long body (L= 1804–1832 µm), a=41–42, relatively short tail (c=10–11 µm), longer outer labial setae (13–14 µm), cephalic setae (4–4.5 µm), arcuate tail tapering almost uniformly, and four caudal setae on the tail. Males have a long body (L= 1870–2014 µm), horn-shaped spicule 36–38 µm long, straight gubernaculum 14–16 µm long, a curved tail tapering almost uniformly, and four caudal setae on the dorsal part of the tail.

Tripylella australis sp. nov. is similar to T. maiuscula and T. minuscula in tail shape, but differs from them by having a longer body (L= 1804–1832 vs 1080–1400 and 860–980 µm, respectively), larger de Man’s ratio a and c values (a=41–42 vs 28–35 and 21–29, c=10–11 vs 6.5–7.6 and 5.7–6.3, respectively), longer outer labial setae (length=13–14 vs 7–9 and 3–4 µm), and in having four caudal setae on the tail (absent in T. maiuscula and T. minuscula).

Tripylella australis sp. nov. differs from all the other species in the genus by body length, tail that uniformly in shape (vs abrupt tapering) and presence of males.

Etymology. Species epithet is named for Australia, from where it was first isolated.