Chthonius euganeus Gardini, 1991

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 : 42-43

Chthonius euganeus Gardini, 1991

( Figs 117–126 , 409 )

Chthonius (C.) euganeus Gardini, 1991: 169 , figs 1–7.

Chthonius mingazzinii Callaini, 1991: 265 , figs Ia–f (n. syn.).

Type locality: Italy, Veneto, Padua Province, Rovolon, Busa de l’Orso 1398 V / PD (45°23’22”N, 11°40’24”E)

Distribution. Italy (Veneto, Romagna).

Diagnosis (♂ ♀). An anophthalmic subterranean Chthonius that differs from other species of the ischnocheles group in the following combination of characters: anterior margin of carapace strongly denticulate, with widely prominent epistome, and with 1 preocular microseta on each side; posterior margin of carapace with 2 macrosetae, without lateral microsetae; chelicerae with 2 or 3 lateral microsetae; chela length 0.97–1.10 mm; chela 5.8–6.35 times as long as deep; chelal fingers with contiguous teeth; fixed and movable chelal fingers with 60–84 and 50–59 teeth respectively; ratio of pedipalpal femur/carapace 1.45–1.55.

Type material of C. euganeus examined. ITALY — Veneto: Padua Prov. — 1 ♂ (holotype), 2 ♀ (paratypes), Rovolon, Busa de l’Orso 1398 V / PD, 43 m a.s.l., 28.V.1983, E. Piva & I. Ferrari leg. ( MSNV) .

Other material examined. ITALY — Veneto: Padua Prov. — 2 ♀, Rovolon, Busa de l’Orso 1398 V / PD, 43 m a.s.l., 28.XII.1991, E. Piva leg. Veneto: Vicenza Prov. — 1 ♀, Alonte, near La Fontana , 45 m a.s.l., 16.VI.1996, E. Piva leg.

Description of adults (♂ ♀). Weak 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 0.9–1.0 times longer than broad, trapezoidal, constricted posteriorly; anterior margin between median macrosetae with denticles and a broad, rather flat epistome in both sexes ( Figs. 117–118 ); no eyes or eye-spots; chaetotaxy m 4m:6:4:2:2(20); length of anteromedian macrosetae 0.10–0.12 mm. Chaetotaxy of tergites 4:4:4:4:6:6:6:6:1T2T1:4:1T2T1:0. Chaetotaxy of sternites 10:(3)8–10(3):(2)7–10(2):7– 8:6: 6: 6: 6:2T1T2:0:2; genital opening of male flanked by 6–9 setae. Chelicerae ( Fig. 119 ) 2.3 (♂ ♀) times as long as broad, palm with 6(7) setae and (2)3 lateral microsetae; fixed finger with 2 distal large teeth followed by 8–10 small teeth proximally reduced in size; movable finger with an isolated subapical tooth (di) at level (♂) or just distad (♀) of the spinneret, followed by a large tooth and 6–10 teeth proximally reduced in size; gs ratio 0.57–0.58; spinneret weakly raised in males, more prominent and rounded in females ( Figs 119–120 ); rallum with 11 blades; serrulae interior and exterior respectively with 14 and 17–18 blades. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 3 + 3 marginal microsetae, II 4, III (5)6(7), IV 6–7; coxa II with 9–10 coxal spines, coxa III with 4–6 coxal spines; intercoxal tubercle bisetose. Pedipalp: femur 5.8 (♂) or 5.7–5.9 (♀) times as long as broad, femoral chaetotaxy 3:6:2:6:1; chela ( Figs 122–123 ) 6.35 (♂) or 5.8–6.15 (♀) times as long as deep; hand of chela 2.1 (♂) or 1.9–2.05 (♀) times as long as deep, long ovoid in dorsal view ( Fig. 121 ); fixed chelal finger with 78–84 (60 in ♀ from Alonte) contiguous teeth, cuspidate and slightly inclined backwards in the distal half of the finger, apically rounded in the proximal half ( Figs 124–126 ); all teeth with dental canal; fixed finger at level of est-it with 10–11 (9 in ♀ from Alonte) teeth occupying 0.1 mm, distance between successive apices 0.009 –0.010 mm (0.011 in ♀ from Alonte); tip of fixed chelal finger with apical sensilla af 1- 2, distal paraxial seta gradually curved and thin; movable chelal finger with 50–59 contiguous teeth, reclined and apically pointed in the distal third of the finger, apically rounded and increasingly reduced towards finger base, reaching back to level of b; between sb and b teeth mainly recognizable by the presence of dental canal ( Figs 124–126 ); movable finger at level of st-t with 9–10 teeth occupying 0.1 mm, distance between successive apices 0.010 –0.011 mm; coupled sensilla pc at level of sb or just distad of sb; tip of movable chelal finger with apical sensilla am 1- 2; trichobothria as in figs 122–123; ratio sb -st/sb -b = 1.3–1.7; ratio of movable finger/hand of chela 2.0 (♂) or 1.9–2.1 (♀); ratio of pedipalpal femur/movable finger 1.0 (♂ ♀); ratio of pedipalpal femur/carapace 1.45–1.55 (♂ ♀).

Measurements (in mm). Body length 1.55–1.6 (♂ ♀). Carapace 0.45 × 0.45 (♂) or 0.44–0.47 × 0.47–0.51 (♀). Chelicerae 0.455 × 0.20 (♂) or 0.47–0.50 × 0.205–0.22 (♀); movable finger length 0.23 (♂) or 0.24–0.26 (♀). Pedipalp: femur 0.70 × 0.12 (♂) or 0.66–0.74 × 0.115–0.13 (♀); chela 1.02 × 0.16 (♂) or 0.97–1.10 × 0.165–0.18 (♀); hand length 0.34 (♂) or 0.31–0.37 (♀); movable finger length 0.68 (♂) or 0.65–0.74 (♀).

Remarks. Chthonius mingazzinii was described by Callaini (1991) from a female collected at Crepaccio, Pietramora near Brisighella (Ravenna Province, Romagna). Crepaccio presumably corresponds to the cave Crepaccio a Ovest di Ca’ Masiera 764 E/ RA. The female holotype is currently unavailable and presumably lost (Callaini, in litt.: April 7, 2019). Morphological characteristics and measurements of the Chthonius euganeus females examined here almost perfectly match the description and figures of C. mingazzinii , apart from the number of coxal spines (coxa II 9–10, III 4–6 in C. euganeus vs. coxa II 6–7, III 2–4 in C. mingazzinii ). Chthonius mingazzinii Callaini, 1991 is therefore proposed as a junior subjective synonym of Chthonius euganeus Gardini, 1991 (n. syn.).

Among the species of the Chthonius ischnocheles group, C. euganeus is morphologically similar to the subterranean C. herminii from which it differs in the following characters: no eyes (anterior eyes with flat lens, posterior eyes absent in C. herminii ); chelicerae with 2 or 3 lateral microsetae (with 1 lateral microseta in C. herminii ); fixed and movable chelal fingers (♂ ♀) with 60–84 and 50–59 teeth respectively (55–62 and 48–52 in C. herminii ); fixed and movable chelal fingers (♂ ♀) at level of est -ist and st -t with 9–11 and 9–10 teeth, respectively, occupying 0.1 mm; distance between successive apices 0.009 –0.011 and 0.010 –0.011 mm respectively (with 6–9 and 6–8 teeth occupying 0.1 mm, distance between successive apices 0.011 –0.017 and 0.012 –0.016 mm, in C. herminii ); ratio of movable finger/hand of chela (♂ ♀) 1.9–2.1 (2.2–2.4 in C. herminii ).

The above description of Chthonius euganeus given here incorporates the previous one by Gardini (1991).

Figures

FIGURES 117–121. Chthonius euganeus Gardini, 1991, Busa de l’Orso (Rovolon, Padua). 117, male holotype, anterior margin of carapace; 118, female paratype, id.; 119, male holotype, left chelicera; 120, female (28.XII.1991), movable finger of left chelicera; 121, female (28.XII.1991), right chelal hand, dorsal view. (Figs 117–119 redrawn after Gardini 1991).

FIGURES 122–126. Chthonius euganeus Gardini, 1991, Busa de l’Orso (Rovolon, Padua). 122, male holotype, left chela, antiaxial view; 123, female paratype, left chela, antiaxial view; 124, female (28.XII.1991), detail of dentition at the right chelal fingers tip, antiaxial view (setae and sensilla af1-2, am1-2 omitted); 125, female (28.XII.1991), detail of fingers at level of trichobothria est-it and st-t, antiaxial view (setae omitted); 126, female (28.XII.1991), detail of fingers at level of trichobothrium sb, antiaxial view (setaeomitted). (Figs 122–123 redrawn after Gardini 1991).

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.