Oligaphorura chankaensis sp. nov.

Figs 16–28

Type material. Holotype female, 2 females and 6 males paratypes. China: Heilongjiang Province: Lake Khanka (alt. ca 70m, 45°19'32" S, 132°31'59" W), litter and soil, Berlese extraction, 18.IX.2011, leg. Wu Haitao and Song Lihong. Holotype and 8 paratypes on slides are deposited in the Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun.

Description. Body color white in alcohol. Size 0.8–0.85 mm in females, 0.7–0.8 mm in males; holotype: 0.8 mm. Body slender and elongated.

Pseudocellar formula dorsally: 43/144/5556(7)4(5–6), ventrally: 11/000/00000; subcoxa 1 of legs I–III with 1 pso each (Figs 17, 22–26). Parapseudocellar formula ventrally 00/000/222301, absent dorsally (Figs 17 & 23); subcoxa 1 of legs I–III with 1, 2 and 2 or 3 psx each (Fig. 17). Pseudopore formula dorsally: 00/011/ 111100, ventrally: 00/111/000 x00 (Figs 17 & 23).

Head. Antennae short and distinctly segmented, as long as head. Length ratio of antennal segments I: II: III: IV = 1: 2: 2: 2. Ant. IV with two distinct thickened S-chaetae, subapical organite with apex globular and basolateral ms just above posterior chaetae (Fig. 19). Ant. III sensory organ composed of 5 papillae, 5 guard chaetae, 2 small sensory rods, 2 granulated sensory clubs, the outer about twice as large as the inner, and a lateral ms (Figs 19–20). Ant. II with 14 chaetae. Ant. I with 9 chaetae. Antennal base with distinct granulation (Fig. 18). PAO located on cuticular furrow built with a 3-lobed vesicle (Fig. 18). Dorsal cephalic chaeta d0 absent, 3+3 p-chaetae between posterior a-pso on head (Fig. 17). Mandible with a strong molar plate and 4 apical teeth. Maxilla bearing 3 teeth and 6 lamellae. Maxillary palp simple with 1 basal chaeta and 2 sublobal hairs. Labral chaetae formula 4/342. Labium with 6 proximal, 4 basomedian (E, F, G, f) and 6 basolateral (a, b, c, d, e, e’) chaetae; labial type ABC, papillae A–E with 1, 4, 0, 3, and 2 guard chaetae respectively (Fig. 21). Postlabial chaetae 4+4 along ventral groove (Fig. 25).

Body chaetotaxy. S-chaetae cylindrical, well differentiated, their formula dorsally: 11/011/222111, ventrally: 11/000/000100 (Figs 17 & 23); subcoxae 2 of legs I, II and III with 0, 0 and 1 S-chaeta, respectively. Smicrochaetae tiny and blunt, present on Th. II–III (Fig. 17). Ordinary chaetae differentiated in meso- and macrochaetae. Th. I tergum with 7+7 chaetae. Th. II–III and Abd. I–III terga with three chaetae on both sides of axial line, without dorsal axial chaetae (Fig. 17). Abd. IV tergum with one or two asymmetric chaetae, Abd. V tergum without axial chaetae, Abd. VI tergum with two axial chaetae (Fig. 17). Th. I, II and III sterna without chaetae.

Appendages. Subcoxa 1 of legs I–III with 4, 5 and 5 chaetae (Fig. 17), subcoxa 2 with 1, 4 and 4 chaetae, respectively. Tibiotarsi of legs I, II and III with 20 (11, 8, 1), 20 (11, 8, 1) and 19 (11, 7, 1) chaetae, respectively (Fig. 22). Unguis without teeth. Unguiculus slender and pointed, 0.6 times as long as inner edge of unguis, with inner basal lamella (Fig. 22). Ventral tube with 6–7+6–7 distal chaetae and 2+2 basal chaetae, without anterior chaetae. Furca reduced to a small cuticular fold with 2+2 dental chaetae in two rows posteriorly; two manubrial rows of chaetae present posteriorly to dental chaetae (Fig. 27).

Female genital plate with 10–13 chaetae (Fig. 23), male genital plate with 26–28 chaetae. Anal valves with numerous acuminate chaetae; each lateral valve with a0 and 2a1; upper valve with chaetae a0, 2b1, 2b2, c0, 2c1, 2c2 (Fig. 28). Anal spines present on indistinct papillae, 0.9 times as long as inner edge of unguis.

Etymology. Named for the name of the lake where we found the new species.

Ecology. Found in coniferous and broad-leaved mixed forest.

Remarks. Oligaphorura chankaensis sp. nov. is similar to the Korean O. montana Weiner, 1994 and the Chinese species O. pseudomontana Sun & Wu, 2012 in having the same characters as following: number of pso on dorsal head and Th. I–Th. III terga (43/144), ventral pso formula (11/000/00000) and pso on subcoxa 1 of legs I–III (1,1,1). But it differs from them by the dorsal pso formula (43/144/5556(7)4(5–6) in the new species versus 43/144/ 54453 in O. montana and 43/144/ 54464 in O. pseudomontana), the ventral psx formula (00/000/ 222301 in the new species versus indistinct in O. montana and 00/000/ 222401 in O. pseudomontana), the ratio of AS /unguis (0.9 in the new species versus 0.75 in O. montana and O. pseudomontana), the lateral tooth of the unguis (absent in the new species versus present in O. montana and O. pseudomontana) and the psx on subcoxa 1 of legs I–III (1, 2, 2 or 3 psx in the new species versus indistinct in O. montana and 1, 1, 1 in O. pseudomontana).