Arrhopalites abchasicus, Vargovitsh, Robert S., 2013

Vargovitsh, Robert S., 2013, Cavernicolous Arrhopalites abchasicus sp. nov. (Collembola: Symphypleona: Arrhopalitidae) from the West Caucasus with a key to the World species of the genus, Zootaxa 3666 (1) : -

Arrhopalites abchasicus sp. nov.

Figs 1–32 , Tables 1 , 2

Diagnosis. Trichobothria ABC form slightly sharp angle close to right and AB> BC. Antenna about 2× of head; Ant III with subbasal swelling; Ant IV with 13 whorls of setae and with 5–7 subsegments indistinctly separated from each other by several annuli. Head dorsum with 4 + 1 + 4 heavily spine-like setae in rows A, B, C and 2 + 2 thickened setae in row D. All claws slender, without tunica, with very small or without inner tooth. Tip of empodium I–III not reaching tip of corresponding claw, all empodia with corner tooth. Tenaculum with 1 seta. Manubrium with 5 + 5 setae; dens with 3, 2, 1, 1, 1 thick anterior setae, Ia is spine-like. Tip of mucro swelled. Circumanal setae thickened and some of them basally serrated; appendices anales rod-like, apically and optionally laterally serrated.

Type material. Holotype on slide “C-800a-7”: female, West Caucasus, Abkhazia, Novy Afon, valley of Psyrtskha River, Psyrtskha Cave, 25.viii.2011, R.S. Vargovitsh leg. Paratypes on slides: 2 males, 16 females, 2 juv. collected together with holotype; 4 females, 17.vi.2006, same cave and collector. Types are deposited in the collection of the Schmalhausen Institute of Zoology, National Academy of Sciences of Ukraine, Kiev.

Besides slides, over hundred specimens are kept in alcohol.

Description. Female: body length (without antennae and furca) about 0.9 mm, completely unpigmented or with spots of weak pale-brownish dorsal pigmentation ( Fig. 23 ).

Head ( Figs 1, 11 , 25 , 31 ). Eyes 1 + 1, unpigmented. Labral / prelabral chaetotaxy: 4 5 5 / 6. Clypeal area (rows a to f) with axial seta in row a. Interantennal area (rows α and β) with axial seta in row β. Dorsal area (rows A to D): 3 axial setae in rows A, B and C; 9 setae are spine-like and with broadened sockets (in row A: 1 + 1, B: 1 + 1, C: 2 + axial + 2); row D with 2 + 2 thickened setae with normal sockets; other setae are not modified.

Antenna ( Figs 18 , 28, 29 ): length about 2× of head. Mean length ratio of antennal segments I: II: III: IV = 1: 2.3: 3.3: 8.2 (1: 2.1: 3: 7.8 in holotype). Ant I with 7 setae of which subapical one is microseta. Ant II with 14 setae. Ant III with subbasal swelling, 18 setae and 2 sense rods in separate pits. Ant IV usually indistinctly subdivided into 5–7 (pseudo)subsegments, separated from each other by 1–5 weakly developed and sometimes hardly visible annuli ( Fig. 28 ); separations are better distinguished in the middle part of the segment and poorly on the basal and apical subsegments. Subsegmental formula depends on number of subsegments and if 6 subsegments present, then formula is: 1 + 4 + 1 = (A + M1) + (M2 – M5) + (B). Ant IV bears 13 whorls of setae.

Foreleg ( Figs 2 , 20 ): precoxae 1, 2 and coxa with 1, 0, 1 setae respectively. Trochanter with 3 anterior and 1 posterior setae; femur with 12 setae, a4 turned perpendicularly to the longitudinal axis of the segment. Tibiotarsus normally with 44 setae: whorl I with 9 setae among which Ja curved and spine-like, each of whorls II–V with 8 setae and region F with 3 primary FP setae (e, ae, pe). Pretarsus with 1 anterior and 1 posterior setulae. Foot complex ( Fig. 27 a). Claw: thin, without tunica, with small and often unnoticeable inner tooth and two pairs of indistinct lateral teeth, 3.8–4.5× shorter than tibiotarsus (4.4 in holotype). Empodium: thin, with corner tooth, 1.4– 1.8× shorter than claw (1.5 in holotype).

Mid leg ( Figs 2 , 21 ): precoxae 1 and 2 with 1, 1 setae respectively, precoxal process present, coxa with 3 setae and microsensillum. Trochanter with 3 simple setae and anterior trochanteral organ; femur with 13 setae, 2 posterior ones are shorter and thinner than others. Tibiotarsus normally with 43 setae: whorl I with 9 setae among which Ja is thick but not curved as in foreleg, whorls II–IV usually with 8 setae, whorl V with 7 setae (Vp absent), region F with 3 FP setae. Foot complex ( Fig. 27 b). Claw: thin, without tunica, inner tooth very small or absent, 2 pairs of small rarely noticeable lateral teeth, 3.8–4.6× shorter than tibiotarsus (4.6 in holotype). Empodium: somewhat broader than in foreleg, with corner tooth, 1.4–1.8× (1.7 in holotype) shorter than claw.

Hind leg ( Figs 2, 10 , 22 ): precoxae 1 and 2 with 1, 1 setae respectively, process on precoxa 1 present, coxa with 3 setae and microsensillum. Trochanter with anterior trochanteral organ, 3 anterior and 1 posterior simple setae; femur with 13 setae, 2 posterior ones as microsetae. Tibiotarsus normally with 44 setae as well as in foreleg but pattern is different: whorl I with 9 setae, whorls II–IV with 8 setae, whorl V with 7 setae (Vp absent), region F with 3 primary setae FP and secondary seta FSa. Foot complex ( Fig. 27 c). Claw: relatively slender, without tunica, without or with vanishingly small inner tooth, with 2 pairs of rarely noticeable lateral teeth, 4.8–5.6× shorter than tibiotarsus (5.2 in holotype). Empodium: broad, corner tooth present, 1.3–1.8× (1.5 in holotype) shorter than claw.

Mean lengths ratio of tibiotarsi I: II: III = 1: 1: 1.2 (in holotype 1: 1: 1.1). Ratio head: tibiotarsus I = 1.5– 1.8 (1.6 in holotype).

Ventral tube ( Fig. 2 ) with 1 + 1 subapical setulae. Tenaculum ( Fig. 15 ): each ramus with 3 teeth and a basal process; anterior lobe with 1 apical setula; tip of posterior lobe is approximately on one level with tip of anterior.

Furca ( Figs 8, 9 , 19 , 32 ): manubrium with 5 + 5 posterior setae, p3 thin and short. Dens (24 setae): anterior side with 3, 2, 1, 1, 1 setae, Ia spine-like, other a and ae setae are heavy. Posterior side with setae Ie, Ii, IIIpi and IVpi moderately spine-like. Mucro ( Fig. 32 ): posterior lamellae serrated with teeth separated from each other or partly accreted, anterior lamella developed, tip broadened and globular. Dens 1.5–1.8× as long as mucro (1.8 in holotype).

Great abdomen ( Fig. 2 ): mesothorax with not modified dorsal setae ( Fig. 6 ). Trichobothrial complex: ABC form about right or slightly sharp angle (67°–91°; 80° in holotype; mean—77°) and AB is 1.3–2.2× longer than BC (1.8 in holotype; mean—1.7). Single p seta of p -row of Abd I is located above the level of trichobothrium B; seta b1 lies almost on line BC, closer to C; microseta c1 (mean length = 5μm) lies in front of and seta c2 —below the trichobothrium C ( Fig. 26 ). Posterior lateral complex with 3 + 3 and furca base complex with 8 setae. Central dorsal complex with 3 subequal setae ( Fig. 7 ). Posterior dorsal complex with 25–29 setae, the longest of which (dI- 1 = 59 μm in holotype) is subequal to hind claw or a little longer ( Fig. 5 ). Ventral complex with 2 (sometimes 1 or 3) setae.

Fifth abdominal segment ( Fig. 2 ) with 2 setae and trichobothrium D in row a, and 2 setae in row p. Genital field with 2 + 2 (sometimes 3 + 3) setae close to anterior margin of genital opening.

Sixth abdominal segment ( Figs 3, 4, 12–14 , 17 , 30 ): cuticular spines uncertain, at most 4 + 4 but often indistinct, incomplete or absent. Circumanal row with 7 broadened setae per side (including axial ms1), some of them serrated near bases. Dorsal valve with 10 + 2 axial + 10 setae, seta ms5 absent. Each of lateral valve bears 19 setae. Appendices anales (36 μm in holotype: Fig. 14 ): rod-like, apically narrowed (sometimes pointed) or as wide as shaft diameter, with apical and sometimes lateral serration, inserted into almost globular papilla. In total, normally 60 setae on Abd VI are present.

Male ( Figs 16 , 24 ; Table 1 ): Chaetotaxy of Abd VI differs from females by shape (no broadened setae), and number (44 setae = 7 + 2 axial + 7 on dorsal valve and 14 + 14 on lateral valves). Genital opening is surrounded by 18 setulae.

Variability. Ant IV differently subdivided (5–7) due to presence and distinctiveness of sutures (rings) between subsegments; in one specimen Ant IV is not subdivided at all. Set of tibiotarsal setae sometimes incomplete: in one female absence of IIa and IIIa on mid leg has been observed. Claws often with almost unnoticeable or absent inner tooth. In one female anterior surface of one dens with additional weak aberrant seta (3, 2, 1, 1, 1, 1). Cuticular spines on Abd VI uncertain or even absent at all. Female appendices anales may be differently serrated: apically with several teeth or bifurcated, laterally smooth or serrated ( Figs 12–14 ).

Bionomy and distribution. Described species inhabits aphotic zone of the cave between the first hall (about 30 m from entrance) and the terminal siphon lake (about 200 m from entrance) with water temperature 12.6°C and air temperature 13.0°C. It prefers humid wooden substratum near pools but also occurs on the water surface. The species coexists with two other representatives of Arrhopalitidae from the genus Pygmarrhopalites. Among ten collembolan species detected from the Psyrtskha Cave A. abchasicus sp. nov. possibly can be classified as a subdominant.

At present the new species is only known from the single cave and has not been found yet in the huge main part of the large karstic system—Novoafonskaya Cave as well as in another sampled cave of the region— Anukhvinskaya Cave.

Etymology. “ abchasicus ” refers to the name of terra typica: Abkhazia.

Ant IV annulations—adjoining subsegments of Ant IV separated by several annuli; S—strongly spine-like; s—weakly spinelike; Emp—empodium; <—tip of Emp not reaching tip of claw;>—tip of Emp overtopping tip of claw.

Remarks. A. abchasicus sp. nov. is moderately troglomorphic species with poor or absent pigmentation, somewhat elongated antennae, slender but not elongated claws. It represents A. caecus species group (with 3, 2, 1, 1, 1 setae on anterior surface of dens: see below about the species groups). Some differences with several species of this group are noted in Table 2 and also can be seen from the key given here to the World species. According to such important diagnostic characters as presence of several annuli between adjoining subsegments of Ant IV, anterodistal seta Ia on dens shaped like a spine, and variable number of cuticular spines on Abd VI, the new species resembles A. karabiensis from caves of the Crimean Peninsula, but readily differs from it by antenna / head ratio, absence of tunica on claw III, length of all empodia which do not reach the tip of corresponding claw, very indistinct inner tooth on claws, absence of seta ms5 on female Abd VI. Absence of ms5 as well as absence of tunica on all claws and similar Ant IV annulations are also known for two other troglobiont species: Caucasian A. macronyx and Crimean A. peculiaris . Both species completely lack cuticular spines on Abd VI, besides, in contrast to the new species: A. macronyx has extraordinary long claws and has no spine-like setae on head dorsum and anterior dens surface; A. peculiaris has 5 spine-like setae on head dorsum, weakly spine-like Ia of dens, more reduced chaetotaxy of Abd VI and neither broadened nor serrated circumanal setae.

Figures

FIGURES 1 – 15. Arrhopalites abchasicus sp. nov.: 1, chaetotaxy of head, frontal view; 2, chaetotaxy of great abdomen, lateral view; 3 – 14, shape of setae: 3, ms 1 of Abd VI; 4, mpi 1 of Abd VI; 5, dI- 1 of great abdomen; 6, dorsal seta of mesothorax; 7, dorsal seta of Abd I; 8, Ia of dens; 9, Ie of dens; 10, trochanteral organ; 11, spine-like seta of head vertex; 12 – 14, appendices anales; 15, tenaculum.

FIGURES 16 – 19. Arrhopalites abchasicus sp. nov.: 16 – 17, chaetotaxy of Abd VI, lateral view: 16, male; 17, female; 18, chaetotaxy of antenna; 19, chaetotaxy of furca, posterior view.

FIGURES 20 – 22. Arrhopalites abchasicus sp. nov.: chaetotaxy of legs, anterior view: 20, foreleg; 21, mid leg; 22, hind leg.

FIGURES 23 – 24. Arrhopalites abchasicus sp. nov.: 23, habitus and pigmentation, alcohol specimen; 24, habitus of male, on slide.

FIGURES 25 – 29. Arrhopalites abchasicus sp. nov.: 25, chaetotaxy of head dorsum; 26, chaetotaxy of trichobothrial complex; 27, foot complex (a—foreleg, b—mid leg, c—hind leg); 28, fragment of Ant IV with annulations between subsegments; 29, Ant II and III.

FIGURES 30 – 32. Arrhopalites abchasicus sp. nov.: 30, fragment of female Abd VI with broadened circumanal setae, lateral view; 31, fragment of head with eye; 32, mucro and distal part of dens, lateral view.

Tables

TABLE 1. Lengths (in µm) for body parts of types of Arrhopalites abchasicus sp. nov.

Body part	Females		Males
	min–max	mean	min–max	mean
Body total	750–1067	930	665–680	672
Head	258–360	314	230–254	242
Antenna	521–760	620	490–536	513
Ant I	39–54	44	30–36	33
Ant II	86–113	98	73–76	74
Ant III	115–173	142	113–128	121
Ant IV	306–450	355	290–297	293
AO-III rods	3.8–6.6	5.3	4.8–4.9	4.9
Tibiotarsus I	160–240	192	165–167	166
Tibiotarsus II	150–240	191	161–162	162
Tibiotarsus III	190–287	228	183–184	184
Claw I	40–53	47	36–38	37
Claw II	40–52	46	34–38	36
Claw III	38–52	44	32–34	33
Empodium I	23–36	30	20	20
Empodium II	23–34	29	20–21	21
Empodium III	25–32	29	19–21	20
Abd seta dI-1	45–62	51	46–49	47
Abd VI longest seta	42–68	54	25–28	27
Appendices anales	25–36	30	absent	absent
Manubrium	125–195	161	127–134	131
Dens	162–214	188	145–153	149
Mucro	95–123	108	86–90	88

TABLE 2. Differences between Arrhopalites abchasicus sp. nov. and similar congeners.

Character	abchasicus caecus karabiensis	loczyi	macronyx	peculiaris tenuis	ulehlovae
Ant/head ratio	2 1.4 1.5–1.6	?	2	2–2.4 1.4	1.3
Ant IV annulations	+ - +	-	+	+ -	-
Head spines	9 13 13	?	-	5?	13
Claw I–III inner tooth	+(-) +(-) +(-) + + + + + +	? +?	- - -	+(-) +(-) +(-) +(-) + +	+ + +
Claw III tunica	- + +	?	-	-?	+
Emp I–III corner tooth	+ + + + + + + + +	? -?	- - +	+ +(-) +(-) + + -	+ + +
Emp/claw tips I–III	<<<<<<>>>	<<<	<<<	<<<<<<	> ≤ ≤
Tenaculum setae	1 1–2 1	?	1–2	1 2	1
Dens seta Ia	S S S	S	usual seta	s S	S
Abd VI seta ms5	- + +	+	-	-?	+
Abd VI spines per side	0–4 4 0–4	2	-	- 0–3	-