Arrhopalites colchicus Vargovitsh, 2025, sp. nov.

Arrhopalites colchicus sp. nov. Figs 3–7, Tables 1–3 http://zoobank.org/ urn:lsid:zoobank.org:act: 9240E584-5369-4C49-95E5-AFFF827113AC Diagnosis (female). Body unpigmented, 0.9 mm long. Eyes not detectable. Setae of head dorsum slender, 3 axial present. Antenna about 2× of head; Ant III with well-developed sense organ; Ant IV subdivided into 6 subsegments weakly separated from each other by 1–3 annuli, with 14 whorls of setae. Trochanter I, II and III with 4, 4, 5 setae. Femur I, II, III with 11, 13, 12 setae. Tibiotarsus I, II, III with 42, 41, 44 setae. Claws slender and extremely elongated, without tunica and without inner tooth; empodia short, without corner tooth. Manubrium with 5 + 5 setae. Dens without distinct spines, posterior side with 16(15) and anterior side with 3, 2, 1, 1, 1 setae, Ia weakly spine-like. Mucro with small slightly knobbed apex, edges of posterior lamellae partly accreted. Trichobothria ABC form about right angle. Posterior setae of great abdomen 4× longer than anterior. Sixth abdominal segment with ordinary smooth not broadened circumanal setae; dorsal valve with 11 + 2 axial setae per side, lateral valve with 16 setae; appendices anales rod-like, smooth, acuminate and apically curved. Belongs to Arrhopalites caecus group of species s. str. (Vargovitsh 2013). Type material. Holotype on slide C-1036a-1: female, W Caucasus, Abkhazia, Sukhum District, Verkhniaya Eshera Vill., Verkhneesherskaya Cave (N 43° 04′ 34″; E 40° 58′ 33″; 540 m a.s.l.), ~ 400 m distance and 60 m depth from entrance, on water surface, 20.vii.2016, R.S. Vargovitsh leg. Paratype on slide C-1036a-2 (Fig. 6A): male, collected together with holotype from the same cave and by the same collector. The holotype and paratype are preserved in the collection of the Schmalhausen Institute of Zoology, National Academy of Sciences of Ukraine, Kyiv. Description. Female. Body length 0.9 mm, unpigmented (see Table 1 and 2 for other measurements). Head (Fig. 3A). Eyes not detected. Clypeal area includes six rows a to f with 4 + axial + 4 / 5 + 5 / 5 + 5 / 5 + 5 /5 + 5 / 6 + 6 setae respectively, and median region M with 4 asymmetrical setae. Interantennal area: row α: 2 + 0 (variable), row β: 1 + axial + 1. Dorsal area with four rows (A to D) with 1 + 1 / 1 + axial + 1 / 2 + axial + 2 / 2 + 2 setae respectively; all setae of head dorsum slender (Figs 4D, 6B). In total, head dorsum bears 3 axial setae (Figs 3A, 6B). Head axial setae (labral, clypeal and dorsal) marked in black in Fig. 3A. Chaetotaxy of the head posterior side as in Fig. 3A (dotted circles). Chaetotaxy of mouth region. Labrum (Figs 3A, 6E): labral (a m p) / prelabral chaetotaxy: 4 5 5 / 6; setae of a-row situated on four labral papillae. Labium: submentum with 4 setae, mentum with 5 setae (Fig. 6F); labial palp (Fig. 3C) with 5 proximal setae, 5 papillae (A, B, C, D, E) with deeply inserted setae and with 13 associated guard setae (a1, b1–4, d1–4, e1–4 of which a1 is blunt and strongly curved) and 3 hypostomal setae (H, h1, h2). Maxilla head as in Fig. 6G. Maxillary outer lobe (Figs 3D, 6E): apical seta of the maxillary outer lobe with short subparallel branch at the base, sublobal plate with three sublobal hairs. Oral fold with 2 setae (Fig. 6E). Antenna (Fig. 3B) 1.9× of head. Length ratio of antennal segments I / II / III / IV = 1 / 2 / 3 / 7.4. Ant I with 7 setae, p as microseta (5.3 μm). Ant II with 14 setae. Ant III without swelling, with following chaetotaxy: 15 simple setae, especially thin Api and Ape setae, 2 well developed sensory rods (11.6 μm) in shallow pits and Aai as small (4 μm) blunt sensillum (Fig. 6D); 20 setae in total. Ant IV indistinctly subdivided into 6 subsegments separated from each other by 1–3 weakly developed and hardly visible annuli. Subsegmental formula: 1 + 4 + 1. Ant IV bears 14 whorls of setae: 4 on apical subsegment (A1–A3 + M1–M2), 4 on median subsegments (M3–M6) and 5 on basal subsegment (BA + BM1–BM3 + BB). Legs. Foreleg (Fig. 4A): precoxae 1, 2 and coxa with 1, 0, 1 setae respectively. Trochanter with 3 anterior and 1 posterior setae. Femur with 11 setae, a4 turned perpendicularly to the longitudinal axis of the segment. Tibiotarsus with 42 setae, tibiotarsal formula: 9, 8, 8, 8, 6, 3; seta Ja of distal whorl I curved and moderately spine-like; whorl V without ai and pi setae; region F with primary setae e, ae, pe. Pretarsus with 1 anterior and 1 posterior setulae. Foot complex (Fig. 7C). Claw: slender and much elongated (91 μm), without tunica, without inner tooth, with a pair of long subapical lateral teeth; about 2.2× shorter than tibiotarsus. Empodium: thin, without corner tooth; very short (1.9× shorter than claw); tip of empodial filament far not reaching tip of claw. Mid leg (Fig. 4B): precoxae 1 and 2 with 1, 1 setae respectively, precoxal process present, coxa with 3 setae and one microsensillum (Fig. 5A). Trochanter with 4 setae: anterior trochanteral organ, 2 anterior and 1 posterior simple setae. Femur with 13 setae. Tibiotarsus with 41 setae (9, 8, 8, 8, 5, 3); Ja curved and moderately spine-like, whorl V without ai and pi setae; region F with primary setae e, ae, pe. Pretarsus with 1 anterior and 1 posterior setulae. Foot complex (Fig. 7D). Claw: slender and much elongated (92 μm), without tunica, without inner tooth and a pair of long subapical lateral teeth; 2.1× shorter than tibiotarsus. Empodium: thin, without corner tooth; very short (2× shorter than claw); tip of empodial filament far not reaching tip of claw. Hind leg (Fig. 4C): precoxae 1 and 2 with 1, 1 setae respectively, process on precoxa 1 present, coxa with 3 setae and one microsensillum. Trochanter with 5 setae: anterior trochanteral organ, 3 anterior and 1 posterior simple setae. Femur with 12 setae, 2 posterior ones (p1 and p3) as microsetae. Tibiotarsus with 44 setae (9, 8, 8, 8, 7, 4); Ja of whorl I as simple seta, region F with primary setae e, ae, pe and secondary seta FSa. Pretarsus with 1 anterior and 1 posterior setulae. Foot complex (Fig. 7E). Claw: slender and elongated (81 μm) but shorter than claw I and II, without tunica, without inner tooth, with pair of relatively long subapical lateral teeth; about 2.7× shorter than tibiotarsus. Empodium: broad, without corner tooth; 1.6× shorter than claw; tip of empodial filament not reaching tip of claw. Lengths ratio of tibiotarsi I / II / III = 1 / 1 / 1.1. Tibiotarsi about 1.6× shorter than head. Ventral tube with 1 + 1 subapical microsetae. Tenaculum (Fig. 5C): each ramus with 3 teeth and basal process; anterior lobe with 1 seta. Furca (Fig. 5B). Manubrium with 5 + 5 posterior setae. Dens with 23–24 setae (8 anterior and 15–16 posterior). 3, 2, 1, 1, 1 setae on anterior side, Ia–IVa, Ba and IIae somewhat thickened, Ia weakly spine-like (Fig. 4K). Posterior side without spine-like setae, Vpe variable (present on one and absent on other dens). Mucro (Fig. 7F): posterior lamellae with teeth partly accreted together, margins look partly wavy or serrated; anterior lamella smooth and well developed; tip rounded or spoon-like but not broadened. Dens 2× as long as mucro (Table 2). Great abdomen (Fig. 5A). Each of segments Th II and III bearing single bent sensillum in row a (13–14 μm) (Fig. 4F) and 3 setae in row m with m1 (Fig. 4E) 3–4× shorter than most posterior setae (dI–dIII)-1 of posterior dorsal complex (Fig. 4G). Anterior part of abdomen with row a (5 setae), row m (4 setae) and seta p. Trichobothrial complex (Figs 5A, 7A): ABC form an angle close to right (74°; 94°) and AB is 1.2× longer than BC; seta p is located above the level of trichobothrium B; seta b1 lies on line BC, closer to C; seta c1 (25 μm) thinner and shorter than c2 but not as microseta, c1 lies in front of trichobothrium C and seta c2—below C. Posterior lateral complex with 5 setae in two rows (2 + 3) and furca base complex with 8 setae in two rows, neosminthuroid seta absent. Central dorsal complex with seta 3 smaller than 1 and 2 (Fig. 7A). Posterior dorsal complex with 18 long setae arranged in 3 longitudinal rows dI–dIII with 6 / 6 / 6 setae respectively, the longest of which (the most posterior setae of rows dI–dIII) = 68 μm is shorter than hind claw (Tables 1, 2). Ventral complex is variable, with one seta on one side of body (Fig. 5A) and two on the other (not shown in Fig. 5A). Small abdomen. Fifth abdominal segment (Fig. 5A) with 2 setae and trichobothrium D in row a, and 2 setae in row p. Genital field with 2 + 2? microsetae along anterior margin of genital opening. Sixth abdominal segment (Figs 5D, 7B) without any cuticular spines. Dorsal valve with 11 + 2 axial + 11 setae. Each of lateral valves (Fig. 7B) bears 16 setae, seta mpi2 of circumanal row absent. Setae of circumanal row slender and not modified, the longest = 45 μm, that is 1.5× shorter than posterior setae of great abdomen (Fig. 4H). Appendices anales (Figs 4I–J; 7B) (24 μm) rod-like, smooth, apically curved and acuminate; sitting on globular basal papilla. Male. 0.85 mm length, slightly smaller than female (Fig. 6A). Antenna 2.1× of head, Ant IV with 7 subsegments separated from each other by 2–4 annuli which are more distinct than in female (Fig. 6C). Both dens with complete set of setae (8 anterior and 16 posterior). Small abdomen (Fig. 5E): dorsal anal valve of Abd VI with 7 + 2 axial +7 setae, ventral valve with 15 setae each, genital opening surrounding with 9 + 9 short setae. Whorl V of left and right tibiotarsus III with 5 and 6 setae respectively. Otherwise, male chaetotaxy corresponds to females; for measurements see Tables 1 and 2. Variability. In female: interantennal area is aberrantly incomplete on the left side (row α: 2 + 0); ventral complex of great abdomen with 1 or 2 setae per side; dens seta Vpe present or absent. In male arrangement of left and right interior dens surface is different: normal 3, 2, 1, 1, 1 and aberrant 3, 1, 2, 1, 1. Ecology and distribution. Two specimens of Arrhopalites colchicus sp. nov. were found on the wat