Scutisotoma trichaetosa Huang & Potapov, 2012, sp. nov.

Scutisotoma trichaetosa sp. nov.

Figs 28–36, Tabs 1 & 2

Material. Holotype, female, China (East), Zhejiang province, near Lin’an, Tianmu Mts., 30°19’N, 119°27’E, 350 m alt., moistened mosses near waterfall, 09.iv.2008, leg. Y. Bu & M. Potapov. Paratypes, 1 male and 3 females, same place. 4 females, Zhejiang province, Lin’an city, near Gongchen Mt., 30°14’N, 119°44’E, 220 m alt., mosses on rock of northern exposition near bridge, 10.iv.2008, leg. Y. Bu & M. Potapov. Type specimens deposited in SIPPE.

Other material. Zhejiang province, near Lin’an, Tianmu Mts., 30°25’N, 119°34’E, 520 m alt., deciduous forest, moss on stones in shadow, 08.iv.2008. Zhejiang province, Shengsi Isl., 30°42’N, 122°28’E, 2 m alt., shingly seashore of Pacific, 22.x.2011, leg. Y. Bu & Y. Gao. Shengsi Isl., Jihu beach, silt and soil under grass on northern slope of rock distant from coast, 6.iv.2009, leg. M. Potapov. Shengsi Isl., Nanchangtu beach, flotation of coarse sand on upper littoral zone under steep forested slope. 6.iv.2009, leg. Y. Bu & M. Potapov.

Description. Size up to 1.0 mm. Colour greyish violet, extremities paler. All abdominal tergites clearly separated. Cuticle with primary granulation only, without pits. Ocelli 8+8, G and H smaller (Fig. 32). PAO wide elliptical, about 2.0–3.0 as long as ocellus diameter and 1.0–1.4 as long as U3. Maxillary outer lobe with 4 sublobal hairs and bifurcate maxillary palp. Maxillary head with short, unmodified lamellae. Labral formula 4/5,5,4. Labium with a full set of papillae and guards. Proximal field with 3 chaetae, basomedian field with 4 chaetae. Ventral side of head usually with 3+3 (rarely 4 on one side) postlabial chaetae (Fig. 34). Ant.1 with 2 basal microsensilla (dorsal and ventral), and 2 ventral sensilla. Ant.2 with 3 bms and 1 laterodistal s. Ant.3 with 1 bms and 6 distal s (2 inner, 2 guards and 2 lateral) (Fig. 36). Sensilla on Ant.4 weakly differentiated, microsensillum and subapical organite present.

Dorsal axial chaetom of Th.II–Abd.III as 6–8, 5–7/4–5, 4–5, 5. Macrochaetae short, weakly differentiated. Medial macrochaetae on Abd.V about half as long as tergite. Thorax without ventral axial chaetae. Sensillary formula 3,3/2,2,2,2,4 (s) and 1,1/1,1,1 (ms). Sensilla short and slightly thickened, on Abd.I–III in almost mid-tergite position. Microsensillum on Abd.III set close to the lateral sensillum (Fig. 28). Sensilla on Abd.V set almost in a line, the most lateral sensillum (accp4) moved slightly forward (Fig. 33). Medial pair of sensilla on Abd.V (accp1 and accp2) about 1.5 times longer than lateral pair (accp3 and accp4).

Unguis simple without inner tooth (Fig. 35). Ti.1–3 with 21,21,25–26 chaetae. B-row of chaetae on Ti.1–2 complete. Tibiotarsal tenent chaetae (1,2,2) clearly clavate, about as long as inner edge of unguis. Femur 1 with 5 a -chaetae, 1 ae -chaeta, 3 e -chaetae, and 7 chaetae of pe-p-pi-i -group (Fig. 3). Upper and lower subcoxa with 2–3 and 5–6 chaetae on leg 2 and 3–4 and 5–6 on Leg 3. Ventral tube with 4+4 (rarely 3 or 5 on one side) laterodistal and 5(4) posterior chaetae. Tenaculum with 4+4 teeth and one chaeta. Anterior furcal subcoxa with 10–14 chaetae, posterior with 6–8 chaetae. Anterior side of manubrium with a pair of distal chaetae, posterior side with 15–16+15–16 (including 3–4+3–4 on laterobasal lobes) (Fig. 30). Dens with 8–9 (6, 10) anterior chaetae. Posterior side with 8–9 chaetae (4–5 in basal group, 1 outer, 2 inner and 1 subapical). Mucro with three teeth, lamellae absent. Ratio of manubrium: dens: mucro = 5.7–7.1: 5.4–6.3: 1.0.

Affinity. Scutisotoma trichaetosa sp. nov. resembles S. kolymica Potapov, Babenko & Fjellberg, 2006 and S. longisensilla Potapov, Babenko & Fjellberg, 2006. They share 2 lateral sensilla on Ant.3, three mucronal teeth, similar chaetotaxy of furca and other features of more common nature. Compared to these congeners, ventrum of S. trichaetosa sp. nov. is more oligochaetotic, i.e. with reduced number of chaetae on postlabial area, femur, posterior side of manubrium, anterior and posterior furcal subcoxa (only adult specimens of new species with fully developed chaetotaxy were studied). 3+3 postlabial chaetae (vs. more common variant of 4+4 or 5+5) is shared only with the members of subarctica group and two North American species of schisti group. Type population of S. kolymica differs from S. trichaetosa sp. nov. in position of ms on Abd. III (Figs 27, 28). The differentiating characters of the three species are summarized in Table 2.

Distribution and ecology. Known from several localities of Zhejiang province (E China), usually in mosses. Name derivation. The new species is named after the presence of 3+3 postlabial chaetae.

Material. Holotype, adult female, Russia (Far East), Khabarovsky Krai (northern part), Ezop Range, Bureinskaya Rassoshina River, mountain tundra (extracted with paradichlorinebenzol), ~ 1800 m alt., leg. A. Brinev & A. Polyakov, 30.vi.06. Paratypes, 9 specimens, the same area, belt of Pinus pumila, litter between stones, ~ 1300 m alt., 02.vii.06; 7 specimens, taiga belt, mosses and lichens near river bank, July 2006, ca 900 m alt., all leg. A. Brinev & A. Polyakov. 20 paratypes: adult and subadult females and males. Type specimens deposited in MSPU.

Description. Size from 0.8 to 1.2 mm. Body stout, cylindrical (Fig. 37). End of abdomen cryptopygiс: Abd.VI hidden under the convex Abd.V. Colour not very dark, blue-violet, extremities paler. Cuticle reticulated. Ocelli 8+8, G and H much smaller (Fig. 38). PAO narrow, with indistinct constriction, 1.3−1.6 as long as U3, almost as long as Ant.1 width (0.8−1.0), three times longer than nearest ocellus (Fig. 38). Maxillary outer lobe with 4 sublobal hairs and bifurcate palp. Maxillary head with short, unmodified lamellae. Labral chaetotaxy as 4/5,5,4. Labium with 3 proximal and 4 basomedian chaetae, papilla Е with full set of guards (e7 present). Ventral side of head with 4+4 (rarely 4+5) postlabial chaetae. Ant.1 with 11 (more rarely 10) chaetae and with 2 basal microsensilla (bms) and 2 sensilla (s), Ant.2 with 3 bms and 1 s, Ant.3 with 1 bms and 5−6 distal s. Number of lateral s depend on sex: females with 1 (Fig. 39), males with 2 lateral sensilla. Male “spurs” on Ant.2−3 present, thin. Sensilla on Ant.4 weakly differentiated, subapical organite small, roundish.

Dorsal axial chaetom of Th.II −Abd.IV as 8−10,5−7/4−5,4−5,4(3),7−8. Common chaetae thick, the most of them moderately serrated on dorsal side of Abd.IV and V (Fig. 41). Thorax without ventral axial chaetae. Macrochaetae pointed, clearly differentiated (Figs 41, 42). Abd.V with several straight and slightly thickened dorsal macrochaetae, about 0.5−0.6 as long as tergite. Abd.IV with 4 macrochaetae of subequal size on each side (Fig. 41). Number of macrochaetae on Th.II −Abd.III 1,1/1+1*,2,2, dorso-lateral macrochaetae on Abd.I weakly developed (notated as 1* in formula). Sensilla on tergites clearly differentiated, significantly shorter and thinner than ordinary chaetae. Sensillar formula 3,3/2,2,2,2,4 (s), 1,1/1,1,1 (ms) (Fig. 37). Sensilla on Abd.I −III in mid-tergal position. Medial and lateral pairs of sensilla on Abd.V similar in size and set in a transversal line (Fig. 41).

Unguis slightly curved, without inner tooth (Fig. 43). Unguiculus about half as long as unguis. Ti.1−3 with 21,21,25–26 chaetae. B-row of chaetae on Ti.1–2 complete. Chaetae x and B5 on Ti. 3 in males thinner than other chaetae. Tibiotarsal tenent chaetae (1−2−2 on Ti.1−3) clavate, on Ti.2−3 of unequal size, longer one 1.1−1.3 as long as U3. Femur 1 with 5 a -chaetae, 1 ae -chaeta, 3 e -chaetae, and 8 chaetae of pe-p-pi-i -group (Fig. 5). Upper and lower subcoxa with 2−3 and 5−7 chaetae on Leg 2 and 5−6 and 5−8 on Leg 3. Ventral tube with 4+4 (rarely 3+3) laterodistal and 5−7 posterior chaetae. Tenaculum with 4+4 teeth and 1 chaeta. Anterior furcal subcoxa with 7−9, posterior one with 5(4−6) chaetae. Furca short (Fig. 41). Anterior side of manubrium without chaetae. Posterior side with 8−10+8−10 on the main part and 3+3 chaetae on laterobasal lobes (Fig. 40). Dens anteriorly with 1 distal chaeta, posterior side almost smooth, with 2 chaetae (two specimens were found with 1 and 3 chaetae on one side). Mucro massive, with two strong teeth, lamellae not differentiated. Ratio of manubrium: dens: mucro = 4.1−5.3: 1.6−1.9: 1.

Affinity. The species is easily identified among congeners by strongly reduced furca on which anterior chaetae absent on manubrium and number of chaetae is strongly reduced on dens. Strong straight macrochaetae are shared with W. echinodermata Potapov, Babenko & Fjellberg, 2006.

Distribution. The species is probably common in tundra and taiga belts of Ezop Range (Far East of Russia).

Name derivation. The new species is named after the shape of the body.