Arrhopalites macronyx

Description. Female: body about 1.2 mm length (holotype 1.23 mm). Coloration (alcohol material): specimens collected in 2010 with usually very weak diffuse reddish-brownish pigment spots on dorsal side, a little more intensive on head dorsum and with very small eye spots (Fig. 25); the largest specimen is pigmented more intensively; specimens collected in 2009 are totally unpigmented. Head (Fig. 1). Eyes uncertain to observe, possibly much reduced: 1 + 1 cuticular swellings and not granulated depressions near them are present but usual corneal lenses were not observed (Fig. 27). Labral chaetotaxy a: 4, m: 5, p: 5; prelabral: 6 (= 6 / 554). Clypeal area with axial seta in row a. Interantennal area: 2 rows (α and β) with axial seta in row β. Dorsal area: 4 rows (from A to D) with 3 axial setae in rows A, B and C; no modified (spine-like) setae (Figs 1, 5). Antennae (Figs 15, 16): length about 2 × (1.8 – 2.3) of head (2.3 in holotype). Mean length ratio of antennal segments I: II: III: IV = 1: 2.2: 3.2: 9 (1: 2.3: 3.5: 9.7 in holotype). Antennal segment I with 6 short setae, subapical one is very small. Ant II with 14 setae. Ant III without swelling, with 18 setae and 2 relatively long (11.6 µm in holotype) and heavy sense rods inserted in a single pit (Figs 15, 29, 30, Table 1); setae Api and Ape short and thin, seta Aai very small and blunt. Ant IV indistinctly subdivided into 7 – 8 subsegments or pseudosubsegments, often separated from each other by 0 – 6 weakly developed and hardly visible annuli which usually increase in number towards distal part of the segment (Figs 16, 31). (Pseudo) subsegmental formula: 1 + 6 + 1; Ant IV bears 14 whorls of setae: 4 on apical subsegment (AI – AIII + M 1), 6 on median subsegments (M 2 – M 6 + BA) and 4 on basal subsegment (BM 1 – BM 3 + BB). Body part Arrhopalites macronyx Troglopalites stygios Foreleg: precoxae 1, 2 and coxa with 1, 0, 1 setae respectively (Fig. 2). Trochanter with 3 anterior and 1 posterior setae; femur with 11 setae, a 4 turned perpendicularly to the longitudinal axis of the segment (Fig. 19). Tibiotarsus (Fig. 22): 3 setae FP present (e, ae, pe); secondary seta FS missing; whorl I with 9 setae among which Ja curved and spine-like; each of whorls II – V with 8 setae but whorl V sometimes incomplete (setae Vai and / or Vpi present or absent). Pretarsus with 1 anterior and 1 posterior setulae. Foot complex (Figs 22, 32 a). Claw: very long and thin, only 1.8 – 2 × shorter than tibiotarsus (1.96 in holotype); without inner tooth, with 2 pairs of lateral teeth: very small subbasal and sharp thin subapical; without tunica. Empodium: thin, somewhat tapered on basal part, 1.8 – 2.2 × shorter than claw, without tooth. Mid leg: precoxae 1 and 2 with 1, 1 setae respectively, precoxal process present, coxa with 2 or 3 setae and microsensilla (Fig. 2). Trochanter with 3 simple setae and anterior trochanteral organ; femur with 12 setae, 2 posterior ones are shorter and thinner than others (Fig. 20). Tibiotarsus (Fig. 23): 3 setae FP present, seta FS missing; whorl I with 9 setae among which Ja curved and spine-like, whorls II – IV with 8 setae, whorl V with 7 setae (Vp absent) but sometimes incomplete (setae Vai and / or Vpi present or absent). Foot complex (Figs 23, 32 b). Claw: very long and thin, only 1.8 – 2 × shorter than tibiotarsus (1.86 in holotype); without inner tooth, with 2 pairs of lateral teeth: very small subbasal and sharp thin subapical; without tunica. Empodium: thin, 1.8 – 2.2 × shorter than claw; without tooth. Hind leg: precoxae 1 and 2 with 1, 1 setae respectively, process on precoxa 1 present, coxa with 3 setae and microsensilla (Fig. 2). Trochanter with anterior trochanteral organ, 3 anterior and 1 posterior simple setae; femur with 12 setae, among them 2 very small posterior setulae (Fig. 21). Tibiotarsus (Fig. 24): 3 setae FP and seta FSa present; whorl I with 9 setae without spine-like ones, whorls II – IV with 8 setae, whorl V with 7 setae (Vp absent) but sometimes incomplete (setae Vai and / or Vpi present or absent). Foot complex (Figs 24, 32 c). Claw: long and thin, but a little shorter than in fore- and mid leg, only 2.3 – 2.5 × shorter than tibiotarsus (2.46 in holotype); without inner tooth, with 2 pairs of lateral teeth: very small subbasal and sharp thin subapical; without tunica. Empodium: broad, 1.3 – 1.5 × shorter than claw; corner tooth present. Mean lengths ratio of tibiotarsi I: II: III = 1: 0.97: 1.08 (in holotype 1: 0.95: 1.08). Mean ratio head: tibiotarsus I = 1.5 (1.48 in holotype). Ventral tube with 1 + 1 subapical setulae. Tenaculum (Figs 13, 14): each ramus with 3 sclerotic teeth and not sclerotized basal process; anterior lobe usually with 1 (as in holotype) or 2 (in 3 specimens) apical setulae; tip of posterior lobe is approximately on one level with tip of anterior. Furca (Fig. 17): manubrium with 5 + 5 setae on posterior side, seta p 2 thin sensilla-like, seta p 3 thin and short. Dens: with distinct subbasal broadening on interior side (Fig. 33); anterior side with 3, 2, 1, 1, 1 setae, Ia – IVa, Ba and IIae are heavy (Figs 9, 17). Posterior side without distinct spines, but setae Ie, Ipe and Ii are thickened at the basis and somewhat spine-like (Figs 10, 17). Mucro (Fig. 34 a – c): posterior lamellae serrated with teeth separated from each other or often looking accreted together; anterior lamella well-developed; tip rounded but not much broadened. Dens 2.1 – 2.3 × as long as mucro (2.23 in holotype). Great abdomen (Fig. 2): mesothorax with slender and curved or S-shaped dorsal setae (Fig. 6). Trichobothria ABC form about right angle (85 o – 101 o; 89 o in holotype) and AB is about 1.4 × (1.2 – 1.6) longer than BC (1.25 in holotype). Single p seta of p-row of Abd I is located above the level of trichobothrium B; seta b 1 lies on line BC, closer to C; seta c 1 small (~ 20 µm) and lies on the level and seta c 2 — below the level of trichobothrium C (Fig. 28). Posterior lateral complex with 2 + 3 and furca base complex with 8 setae. Central dorsal complex with three setae of which seta 3 is more than 3 × shorter than two others (Fig. 35). Posterior dorsal complex with about 15 setae the longest of which is about 1.5 × shorter than hind claw (Figs 7, 8). Ventral complex with 1 or 2 (rarely 0) setae. Fifth abdominal segment with 2 setae and trichobothrium D in row a, and 2 setae in row p (Fig. 2). Genital field with 2 + 2 setae close to anterior margin of genital opening. Sixth abdominal segment (Fig. 18): without cuticular spines; circumanal setae (Figs 3, 4, 18, 36): broadened without serration (ms 1, mpi 3), winged and serrated subbasally (usually mps 1 – mps 3 and mpi 1 – mpi 2) or simple (mpi 4). Seta ms 5 on dorsal valve is absent. Dorsal valve bears 10 + 2 axial + 10 setae, each of lateral valve bears 17 setae (totally 56 setae on Abd VI). Appendices anales (44.8 µm in holotype) rod-like, smooth, gradually narrowed, curved in distal half, with acuminated tip, inserted into semiglobular papilla (Figs 11, 12). Male: smaller than females, body length is about 1 mm or less (Table 1). Chaetotaxy is the same as in females except Abd VI (Fig. 2) with no broadened or winged setae, with 7 + 2 axial + 7 setae on upper anal valve, 13 setae on each of lateral valves (totally 42 setae on Abd VI versus 56 in female) and different chaetotaxy around genital opening on Abd V (about 10 setulae versus 4 in females). Variability. Ventral complex of great abdomen includes 1 or 2 (rarely asymmetrically 0) setae. Seta Vpe of dens present or absent. Tenaculum with 1 or 2 setae. Setae Vai and / or Vpi on tibiotarsi sometimes absent. Corner tooth of empodium III in 1 specimen absent. Two males possess 7 + 2 axial + 6 setae on dorsal anal valve with seta ms 2 asymmetrically present / absent. Bionomy and distribution. Specimens of the new species were sampled about 100 m from the entrance exclusively on the water surface of small subterranean flow lake and on wet speleothems just near the lake. The water and air temperature was 9.9 o C. Terrestrial hand sampling and Barber’s traps in the same cave provided another species of Arrhopalitidae but not A. macronyx sp. nov. This fact, together with morphological characters (long thin claws and mucro with partly accreted teeth and well-developed anterior lamella) supports an opinion about epineustonic and hygropetric mode of life of the new species in subterranean ecosystem. The species was found only in one of 45 sampled caves of the Western Caucasus and most likely represents a narrow troglobiont endemic.

Diagnosis. Trichobothria ABC form about right angle and AB> BC. Antenna about 2 × of head; Ant IV with 14 whorls of setae and with 8 (pseudo) subsegments indistinctly separated from each other by several annuli. No spiny setae on head. All claws much elongated and thin, without tunica and inner tooth; fore and mid claw 2 × shorter than tibiotarsus. Empodia much shorter than claws, only empodium III with small corner tooth. Manubrium with 5 + 5 setae; dens without distinct spines, with 3, 2, 1, 1, 1 thick anterior setae. Tip of mucro rounded but not broadened; posterior lamellae serrated with teeth often accreted together, anterior lamella well-developed. Small abdomen without cuticular spines; circumanal setae winged and serrated basally; appendices anales rod-like, curved, apically acuminated.

Remarks. A. macronyx sp. nov. can be compared with species of Arrhopalites without cuticular spines on Abd VI, with anterior dens formula 3, 2, 1, 1, 1 and without strong anterior distal spine on dens: A. coreanus Park & Kang, 2007, A. minor Park & Kang, 2007, A. pukouensis Wu & Christiansen, 1997, A. peculiaris Vargovitsh, 2009 and A. gul Yosii, 1966. The first three have short antennae with undivided Ant IV, strongly spine-like distolateral seta on dens and claws neither elongated nor thinned. The latest two share with the new species elongated antennae with annuli between subsegments of Ant IV and troglomorphic claws. Besides, as well as new species A. gul has no strongly spine-like setae on dens and has winged circumanal setae. From A. gul the new species differs by absence of spiny setae on head dorsum, presence of corner tooth on hind empodium, antennae: head ratio 2 × (3 × in A. gul), and not broadened tip of mucro. Differences with A. peculiaris are: very long claws (thinned but not elongated in A. peculiaris), absence of cephalic spiny setae (5 spines in A. peculiaris), size of seta c 1 of trichobothrial complex (about 20 µm in macronyx versus about 8 µm in peculiaris), broadened and serrated circumanal setae, absence of strongly spine-like setae on dens, shape of mucro and antennal organ of third antennal segment (Table 2). A. macronyx ~ right 2 7 – 8 14 10 – 13 - 1.5 A. peculiaris ~ right 2 – 2.4 6 – 7 15 7 – 9 5 1.3 – 1.5 A. gul? 3 7 14? +? continued. Species Tita: Cl I, III Emp tooth I, II, III Tr III setae App anal Abd VI circ T. stygios 3, 4 0, 1, 1 4 br, ser simple A. macronyx 2, 2.5 0, 0, 1 5 ac, sm, cu L, b-ser A. peculiaris 4.5, 6 1 (0), 1 (0), 1 (0) 5 br, ser simple A. gul? 0, 0, 0; (rarely 1)? rod, bl L, b-cil ABC — trichobothria; H — head; ss — subsegments; AO-III — sense organ of third antennal segment, length is given for females only; Tr — trochanter; Tita — tibiotarsus; Cl — claw; Emp — empodium; App anal — female appendices anales: ac — acuminated, bl — blunt, br — gradually broadened, cu — curved, sm — smooth, ser — serrated, rod — rod-like; circ — circumanal setae: Llamellate, b-ser — serrated near base, b-cil — ciliated near base.

Etymology. “ macronyx ” from Greek ‘ μάĸρος’ — big, long and ‘ όνυξ’ — claw. The name denotes extraordinary long claws (up to 154 µm: Fig. 32 d), possibly the longest among the known species of the genus Arrhopalites).

Type material. Holotype on slide “ C- 698 - 5 ”: female (Fig. 26), Western Caucasus, Abkhazia, Gudauta District, Gumishkha Massif, about 5 km north-east from Novy Afon, Anukhvinskaya Cave, 580 m a. s. l., 25. viii. 2009, R. S. Vargovitsh leg. Paratypes on slides: 2 males, 10 females, Anukhvinskaya Cave, 25. viii. 2009, R. S. Vargovitsh leg.; male, female, same cave and collector, 22. viii. 2010. Types are preserved in SIZNAS. Besides slides, 62 specimens are kept in alcohol.