Metachelifer takensis, Li & Shi, 2022

Li, Yun-Chun & Shi, Ai-Min, 2022, Cave-inhabiting Cheliferidae (Arachnida, Pseudoscorpiones) from Thailand, with description of four new species of Metachelifer Redikorzev, ZooKeys 1103, pp. 171-188 : 171

Metachelifer takensis sp. nov.

Figs 3 , 6A, B

Type material.

Holotype male: Thailand, Tak Province, Umphang district, Umphang subdistrict, Huai Lao Poo Cave, 15°57.680'N, 098°52.510'E, 534 m a.s.l., 16 Nov 2016, Yun-Chun Li and Zhi-Gang Chen leg, in MCWNU (Ms20161116-01). Paratypes: 1 male, 1 female, 4 tritonymphs, collected with the holotype, in MCWNU (Ms20161116-01).

Diagnosis.

Troglobiont habitus. This new species is distinguished from other members of the genus Metachelifer by the following combination of characters: coxa IV with 45-50 setae; movable finger with 2 pseudotactile setae; male anterior genital operculum with 75-80 setae (without tubular setae); female anterior genital operculum with 22 setae (without tubular setae), posterior operculum with 8 lyrifissures.

Etymology.

Latinized adjective, derived from the province of Tak, where the type locality is located.

Description.

Adult male (Fig. 6A ). Carapace, pedipalps and tergites dark brown, remaining parts yellowish brown (Fig. 6 A ).

Carapace (Fig. 3A ): 1.06-1.08 × longer than broad, with a pair of well-developed eyes, length of eyes 0.11 mm, breadth 0.05 mm, carapace surface evenly and strongly granular. Median and posterior furrows prominent, regularly granular. Dorsal setae of carapace, borne on larger but relatively inconspicuous tubercles. With 95-96 denticuloclavate setae, including 6 on anterior margin and 11-12 on posterior margin. Coxae: manducatory process with a total of 4 setae (1 long apical, 1 rather short subapical seta, and 2 suboral setae at base of medial margin). Pedipalpal coxa with 11-12 (non-denticulate) + 6-7 (denticulate) setae, coxa I 13-15, II 15-17, III 15-19, IV with an anterolateral process and 45-50 setae. Coxal sac occupying only 2/5 of coxal length, atrium well developed (Fig. 3E ). Chelicera (Fig. 3B, C ): 1.75-1.80 × longer than broad, hand with 5 setae and 1 lyrifissure dorsally, movable finger with 1 submedial seta and 1-2 teeth (Fig. 3B ). Galea with 3 short branches (Fig. 3B ). Serrula exterior with about 17-18 blades. Rallum with 3 blades, anterior one weakly denticulate distally (Fig. 3C ). Pedipalp (Figs 3F-H ): all segments with well-developed granulation, except for chelal fingers, which are smooth; dorsal setae short and prominently denticuloclavate. Trochanter 2.00-2.01 × longer than broad, femur 6.04-6.06 × longer than broad, patella 4.64-4.65 × longer than broad, femur 1.16-1.17 × longer than patella. Chela with pedicel 5.94-5.97 × longer than broad, hand with pedicel 2.97-2.99 × longer than broad; movable finger 1.02-1.03 × longer than hand with pedicel length. Fixed finger with 61-62 small cusped teeth, movable finger with 62 teeth; venom apparatus present in both chelal fingers, very short (Fig. 3G ). Fixed chelal finger with 8 trichobothria and movable finger with 4, eb - esb (retrolateral view) and ib-isb (dorsal view) at the base of the fixed finger; est in finger middle, et distinctly closer to fingertip than to it; on movable finger, with two pseudotactile setae, one nearer fingertip, one nearer t and on same level, st nearer to sb than to t. Opisthosoma: tergal chaetotaxy (I-XI): 12: 15: 13: 14: 13: 21: 16: 18: 15: 14: 13; sternal chaetotaxy (IV-XI): 2 × 1 + 9: 12: 14: 13: 12: 11: 8: 11; anal cone with 2 dorsal and 2 ventral setae. Tergite XI with 2 tactile setae. Because only two specimens were available for the study, the structure of the genitalia could not be examined in detail. It was only possible to see well visible eversible sacs (ramshorn organs). Anterior genital operculum with 75-80 setae (without tubular setae) and 2 lyrifissures; posterior operculum with 16 setae, 8 lyrifissures (Fig. 3I ). Legs: Leg I: surface with weak scale-like sculpture, trochanter 1.39-1.40 ×, femur 1.53-1.55 × longer than deep and 0.43-0.45 × longer than patella; patella 4.29-4.32 ×, tibia 4.75-4.77 ×, tarsus 5.67-5.70 × longer than deep, subterminal seta simple, claws modified and asymmetrical, lateral claw shorter than mesal one (Fig. 3D ). Leg IV: trochanter 1.77-1.79 ×, femoropatella 3.39-3.41 ×, tibia 6.92-6.95 × longer than deep and tarsus 6.56-6.58 × longer than deep. Arolia on legs I and IV shorter than claws (Fig. 3D ).

Adult female (Fig. 6B ). Mostly the same as the holotype.

Carapace: slightly longer than broad (1.10 ×), anterior margin with 4 setae, posterior margin with 10 setae. Well-developed paramedian impressions behind eyes like in male. Coxae: pedipalpal coxa with 14 (non-denticulate) + 4 (denticulate) setae, coxa I 11, II 15, III 23, IV 46. Chelicera: 1.79 × longer than broad, movable finger with 2 teeth. Pedipalp: trochanter 1.88 × longer than broad, femur 6.04 × longer than broad, patella 4.37 × longer than broad, femur 1.15 × longer than patella. Chela with pedicel 5.31 × longer than broad, hand with pedicel 2.71 × longer than broad; movable finger 1.01 × longer than hand with pedicel length. Opisthosoma: tergal chaetotaxy (I-XI): 14: 16: 14: 17: 20: 18: 19: 20: 18: 14: 13; sternal chaetotaxy (IV-XI): 2 × 1 + 11: 13: 14:14: 13: 12: 10: 10; anal cone with 2 dorsal and 2 ventral setae. Anterior genital operculum with 22 setae (without tubular setae) and 2 lyrifissures; posterior operculum with 12 setae, 8 lyrifissures (Fig. 3J ). Sternites with 2 lateral cribriform plates.

Dimensions

(length/width or, in the case of the legs, length/depth in mm). Males (female in parentheses): body length 3.63-3.75 (3.52). Carapace 1.05-1.06/0.99-1.00 (1.11/1.01). Pedipalp: trochanter 0.60-0.62/0.30-0.31 (0.60/0.32), femur 1.51-1.53/0.25-0.26 (1.51/0.25), patella 1.30-1.32/0.28-0.29 (1.31/0.30), hand with pedicel 1.07-1.09/0.36-0.38 (1.14/0.42), length of movable chelal finger 1.09-1.10 (1.15), length of chela 2.14-2.17/0.36-0.38 (2.23/0.42). Chelicera: 0.32-0.34/0.19-0.20 (0.25/0.14). Leg I: trochanter 0.25-0.26/0.18-0.19 (0.25/0.19), femur 0.26-0.28/0.17-0.18 (0.35/0.18), patella 0.60-0.62/0.14-0.15 (0.62/0.15), tibia 0.57-0.59/0.12-0.13 (0.62/0.15), tarsus 0.51-0.52/0.09-0.10 (0.53/0.08). Leg IV: trochanter 0.39-0.41/0.22-0.23 (0.42/0.21), femoropatella 0.95-0.97/0.28-0.29 (1.05/0.29), tibia 0.90-0.92/0.13-0.14 (0.92/0.13), tarsus 0.59-0.60/0.09-0.10 (0.61/0.09).

Distribution.

Thailand (Tak).

Figures

Figure 3. Metachelifer takensis sp. nov., holotype male (A-I) and paratype female (J) A carapace B left chelicera C rallum of left chelicera D detail on tarsus I, lateral view E coxa IV, ventral view F palp (minus chela) G chela, retrolateral view H chela, dorsal view I male genital area J female genital area. Scale bars: 0.50 mm.

Figure 6. A, B Metachelifer takensis sp. nov., dorsal views A holotype male B paratype female C, D M. thailandicus sp. nov., dorsal views C holotype male D paratype female. Scale bar: 1.00 mm (A-D).