Chthonius gentianae, Gardini, 2021

Gardini, Giulio, 2021, The Italian species of the Chthonius ischnocheles group (Arachnida, Pseudoscorpiones, Chthoniidae), with reference to neighbouring countries, Zootaxa 4987 (1), pp. 1-131 : 48-49

Chthonius gentianae n. sp.

( Figs 135–142 , 409 )

Type locality: Italy, Veneto, Treviso Province, Fregona, Pian del Cansiglio, Bus della Genziana 1000 V / TV (46°03’27”N, 12°24’00”E) .

Distribution. Italy (Veneto).

Diagnosis (♂). An anophthalmic hypogean Chthonius that differs from other species of the ischnocheles group in the following combination of characters: anterior margin of carapace without preocular microsetae; posterior margin with 2 macrosetae, without lateral microsetae; tergite I with 2 setae; chelicerae with 2 lateral microsetae; chela length 1.36 mm; movable chelal finger length 0.93 mm; chela 6.8 times as long as deep; chelal fingers with reclined, pointed and widely spaced teeth; fixed and movable chelal fingers with 52 and 47 teeth, respectively; ratio of pedipalpal femur/carapace 1.75.

Type material. ITALY — Veneto: 1 ♂ (holotype: in poor conditions, without left palpal chela), Treviso Prov., Fregona, Pian del Cansiglio , Bus della Genziana 1000 V / TV (46°03’27”N, 12°24’00”E), 1013 m a.s.l., 3.X.1985 , S. Zoia, R. Sciaky & E. Piva leg. ( MHNG) .

Derivatio nominis. Gentiana , a genus of plants belongings to the family Gentianaceae , is also the name of the cave Bus della Genziana, the type locality of the species.

Description of adults (♂; ♀ unknown). Highly specialized troglomorphic facies; integument slightly pigmented, carapace, tergites, chelicerae and pedipalps pale reddish brown; weak hispid granulation on lateral surfaces of carapace, on cheliceral palm and on base of fixed chelal finger. Carapace ( Fig. 136 ) 1.0 times longer than broad, trapezoidal, constricted posteriorly; anterior margin denticulate between median macrosetae and without an evident epistome ( Fig. 135 ); ocular area as in fig. 136, no eyes or eye-spots; chaetotaxy 4:6:4:2:2(18), setae long and thin, length of anteromedian macrosetae 0.19 mm. Chaetotaxy of tergites 2:3:4:4:6:6:6:6:1T2T1:4:1T2T1:0. Chaetotaxy of sternites: not seen; genital opening of male flanked by 8 setae on each side. Chelicerae ( Fig. 137 ) 2.35 times as long as broad, palm with 6 setae and 2 lateral microsetae; fixed finger with 9 teeth; movable finger with an isolated subapical tooth (di) located more proximal with respect to the spinneret, and 8 teeth proximally reduced in size; gs ratio 0.53; spinneret triangular, prominent, acute angle-shaped; rallum with 11 blades; serrula exterior with 18 blades. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 3 + 2–3 marginal microsetae, II 3–4, III 6, IV 5–6; coxa II with 9–10 coxal spines, coxa III with 4–5 coxal spines; intercoxal tubercle bisetose. Pedipalp: femur 7.5 times as long as broad, femoral chaetotaxy 3:5:3:5:1; chela ( Fig. 139 ) 6.8 times as long as deep; hand of chela 2.15 times as long as deep, with parallel sides in dorsal view ( Fig. 138 ); fixed chelal finger with 52 teeth: 5 distal teeth small, triangular and slightly reclined, 38 large, apically pointed, long reclined teeth increasingly reduced towards the finger base, and 9 low and rounded teeth proximally ( Figs 140–142 ), all teeth with dental canal; base of fixed chelal finger with few microtubercles; fixed finger at level of est-it with 5 teeth occupying 0.1 mm, distance between successive apices 0.021 –0.023 mm; tip of fixed chelal finger with apical sensilla af 1- 2, distal paraxial seta gradually curved and thin; movable chelal finger with about 47 teeth, reclined and apically pointed in the distal third of the finger, apically broadly rounded and increasingly reduced towards finger base, reaching back near b (between sb and b they are recognizable only by the presence of dental canal) ( Figs 140–142 ); movable finger at level of st-t with 6 teeth occupying 0.1 mm, distance between successive apices 0.018 –0.020 mm; coupled sensilla pc just proximad of sb; tip of movable chelal finger with apical sensilla am 1- 2; trichobothria as in fig. 139; ratio sb -st/sb -b = 1.95; ratio of movable finger/hand of chela 2.15; ratio of pedipalpal femur/movable finger 1.0; ratio of pedipalpal femur/carapace 1.75.

Measurements (in mm). Body length 1.7. Carapace 0.53 × 0.52 (0.50 anteriorly). Chelicerae 0.53 × 0.225; movable finger length 0.27.Pedipalp:femur 0.935 × 0.125; chela 1.36 ×0.20; hand length 0.43; movable finger length 0.93.

Remarks. Among the species of the Chthonius ischnocheles group, C. gentianae n. sp. may be related to the epigean C. carinthiacus that is present in the same geographical area. Both species share the same chelal tooth pattern, the absence of preocular microsetae and 2 macrosetae on the posterior margin of carapace but no lateral microsetae. They differ in the number of lateral microsetae on the chelicera (2 in C. gentianae , 1 in C. carinthiacus ) and for evident adaptive characters: no eyes (anterior eyes with convex lens, posterior ones with flat lens in C. carinthiacus ); chela 6.8 times as long as deep (5.1–5.75 times in males of C. carinthiacus ); chela length 1.36 mm (0.72–0.83 mm in males of C. carinthiacus ); movable chelal finger length 0.93 mm (0.46–0.54 mm in males of C. carinthiacus ); fixed chelal finger with 52 teeth (with 28–41 teeth in males of C. carinthiacus ).

Figures

FIGURES 135–138. Chthonius gentianae n. sp., male holotype. 135, anterior margin of carapace; 136, carapace; 137, right chelicera; 138, left chelal hand, dorsal view.

FIGURES 139–142. Chthonius gentianae n. sp., male holotype. 139, left chela, antiaxial view; 140, detail of dentition at the left chelal fingers tip, antiaxial view; 141, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 142, detail of fingers at level of trichobothrium sb, antiaxial view.

FIGURES 406–409. Distribution maps forthe Italian species of the Chthonius ischnocheles group.406, Chthonius densedentatus Beier, 1938; 407, Chthonius ischnocheles (Hermann, 1804); 408, Chthonius pygmaeus Beier, 1934; 409, Chthonius euganeus Gardini, 1991, Chthonius gentianae n. sp., Chthonius herminii n. sp. and Chthonius paolettii Beier, 1973.