Chthonius multidentatus Beier, 1963

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 : 102-103

Chthonius multidentatus Beier, 1963

( Figs 320–334 , 410 )

Chthonius (C.) multidentatus Beier, 1963a: 254 , fig. 1.

Type locality: Italy, Sicily, Siracusa Province, Siracusa, Grotta Monello 7007 Si /SR (37°01’06”N, 15°09’52”E) .

Distribution. Italy (Sicily).

Diagnosis (♂ ♀). An anophthalmic hypogean Chthonius that differs from other species of the ischnocheles group in the following combination of characters: anterior margin of carapace with 1 preocular microseta on each side; posterior margin of carapace mostly with 2 macrosetae and 1 lateral microseta on each side; chelicerae with 2 lateral microsetae; chela length 1.0– 1.3 mm; movable chelal finger length 0.68–0.92 mm; chela 6.1–6.3 times as long as deep; chelal fingers with contiguous teeth; fixed and movable chelal fingers with 83–97 and 60–77 teeth respectively; fixed and movable chelal fingers at level of est -ist and st -t, respectively, with 11–12 and 7–10 teeth occupying 0.1 mm, distance between successive apices 0.008 –0.009 and 0.010 –0.014 mm respectively; ratio of pedipalpal femur/carapace 1.35–1.55.

Type material examined. ITALY — Sicily: 1 ♀ (holotype), “Grotta Monello (Siracusa), 7.X.1962, Alicata leg.” “ Chthonius (C.) multidentatus n. sp., det. Beier, Type! ♀ ” ( MSNV) .

Other material examined. ITALY — Sicily: Siracusa Prov. —2 D, Siracusa, Grotta del Conzo 7005 Si /SR, 115 m a.s.l., 4.II.2019, G. Nicolosi leg.; 1 ♂ 1 ♀ , id., 26. VI.2019, G. Nicolosi leg.; 1 ♂ 14 ♀, id., 26.IX.2019, G. Nicolosi leg.

Description of adults (♂ ♀). 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 the fixed chelal finger. Carapace ( Fig. 322 ) 0.90–0.95 times longer than broad, trapezoidal, constricted posteriorly; anterior margin denticulate between median macrosetae and with a widely prominent epistome ( Figs 320-321 ); ocular area as in fig. 322, no eyes or eye-spots; chaetotaxy m 4m:6:4:2:m 2m (22), rarely (1 ♀) m 4m:6:4:2:4(22). Chaetotaxy of tergites 4:4:4:4:(5)6:6:6:6:1T2T1:4:1T2T1:0. Chaetotaxy of sternites 10:(3)8(3):(2)8(2):8–9:6:6:6:6:2T1T2:0:2; genital opening flanked by 7 setae on each side. Chelicerae ( Fig. 323 ) 2.1–2.2 times as long as broad, palm with 6 setae and 2 lateral microsetae; fixed finger with 2 distal large teeth followed by 9 small teeth; movable finger with an isolated subapical tooth (di) at level with the spinneret, followed by a large tooth and 8–10 teeth proximally reduced in size; gs ratio 0.62–0.65; spinneret weakly raised in both sexes ( Figs 323–324 ); rallum with 11 blades; serrulae interior and exterior with 15 and 17 blades respectively. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 3(4) + 3 marginal microsetae, II 4, III 5, IV 6; coxa II with 5–10 coxal spines, coxa III with 5–6 coxal spines; intercoxal tubercle bisetose. Pedipalp: femur 5.5 (♂) or 5.4–5.6 (♀) times as long as broad, femoral chaetotaxy 3:6:2(3):5:1; chela ( Figs 327, 331 ) 6.25 (♂) or 6.1–6.3 (♀) times as long as deep; hand of chela 2.05 (♂) or 2.0 (♀) times as long as deep, with a long ovoid profile in dorsal view ( Fig. 325– 326 ); fixed chelal finger with 83 (♂) or 95–97 (♀) contiguous teeth, all cuspidate and slightly inclined backwards in the distal two thirds of the finger, apically rounded in the proximal one ( Figs 328–330, 332–334 ), all teeth with dental canal; fixed finger at level of est-it with 11–12 teeth occupying 0.1 mm, distance between successive apices 0.008 –0.009 mm; tip of fixed chelal finger with apical sensilla af 1- 2, distal paraxial seta gradually curved and thin; movable chelal finger with 60 (♂) or 71–77 (♀) contiguous teeth, reclined and apically pointed in the distal half of the finger, rounded in the proximal half of the finger and increasingly reduced from sb towards the finger base, the proximal teeth recognizable only by the presence of dental canal ( Figs 328–330, 332–334 ); movable finger at level of st-t with 7–10 teeth occupying 0.1 mm, distance between successive apices 0.010 –0.014 mm; coupled sensilla pc just distad of sb; tip of movable chelal finger with apical sensilla am 1- 2; trichobothria as in figs 327, 331; ratio sb -st/sb -b = 2.0–2.1; ratio of movable finger/hand of chela 2.05–2.2 (♂ ♀); ratio of pedipalpal femur/movable finger 0.95–1.0 (♂ ♀); ratio of pedipalpal femur/carapace 1.35–1.55 (♂ ♀).

Measurements (in mm). Body length 1.5 (♂) or 2.0 (♀). Carapace 0.445 × 0.48 (0.45 anteriorly) (♂) or 0.54– 0.64 × 0.60–0.68 (0.57–0.65 anteriorly) (♀). Chelicerae 0.48 × 0.215 (♂) or 0.60 × 0.28 (♀); movable finger length 0.25 (♂) or 0.295 (♀). Pedipalp: femur 0.66 × 0.12 (♂) or 0.85–0.87 × 0.15–0.16 (♀); chela 1.0 × 0.16 (♂) or 1.26– 1.30 × 0.205–0.21 (♀); hand length 0.33 (♂) or 0.41–0.43 (♀); movable finger length 0.68 (♂) or 0.86–0.92 (♀).

Remarks. Among the species of the Chthonius ischnocheles group, C. multidentatus is morphologically similar to the subterranean C. caoduroi from Basilicata, C. gallettii from Sicily, and C. inguscioi from Apulia.

Chthonius multidentatus differs from C. caoduroi in the following main characters: no eyes (anterior eyes with flat lens, posterior eyes reduced to a pale cuticular area in C. caoduroi ); tergite I with 4 setae (2 or 3 setae in C. caoduroi ); fixed and movable chelal fingers with 83–97 and 60–77 teeth respectively (64–71 and 39–53 in C. caoduroi ); fixed and movable chelal fingers at level of est -ist and st-t, respectively, with 11–12 and 7–10 teeth occupying 0.1 mm, distance between successive apices 0.008 –0.009 and 0.010 –0.014 mm respectively (with 6–7 and 5 teeth occupying 0.1 mm, distance between successive apices 0.014 –0.014 and 0.018 –0.020 mm respectively, in C. caoduroi ); ratio of pedipalpal femur/carapace 1.35–1.55 (1.6–1.7 in C. caoduroi ).

Chthonius multidentatus differs from C. gallettii in the following main characters: no eyes (anterior eyes with flat lens, posterior eyes reduced to a pale cuticular area in C. gallettii ); anterior margin of carapace with 1 preocular microseta on each side (2 preocular microsetae in C. gallettii ); male chela length 1.0 mm, 6.25 times as long as deep (1.52 mm, 7.4 times as long as deep in C. gallettii ); fixed and movable chelal fingers of male with 83 and 60 teeth, respectively (70 and 50 teeth in C. gallettii ).

Chthonius multidentatus differs from C. inguscioi in the following main characters: no eyes (anterior eyes with flat lens, posterior eyes reduced to a pale cuticular area in C. inguscioi ); anterior margin of carapace with 1 preocular microseta on each side (2 preocular microsetae in C. inguscioi ); fixed and movable chelal fingers of male with 83 and 60 teeth respectively (68–77 and 53–56 teeth in C. inguscioi ).

The above redescription of Chthonius . multidentatus agrees with the one of Beier (1963a), except for the chelal length/width ratio of female that is given as 6.5 in Beier (1963a) but 6.1–6.3 (length/depth) in the present study.

The caves Grotta Monello, type locality of C. multidentatus , and Grotta del Conzo, the second known locality of the species, are located near each other in the same karst complex.

Figures

FIGURES 320–326. Chthonius multidentatus Beier, 1963, Grotta del Conzo, 26.VI.2019 (Syracuse). 320, male, anterior mar- gin of carapace; 321, female, id.; 322, male, carapace; 323, male, right chelicera; 324, female, movable finger of right chelicera; 325, male, right chelal hand, dorsal view; 326, female, id.

FIGURES 327–334. Chthonius multidentatus Beier, 1963, Grotta del Conzo, 26.VI.2019 (Syracuse). 327, male, right chela, antiaxial view; 328, male, detail of fingers at the chelal tip, antiaxial view; 329, male, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 330, male, detail of fingers at level of trichobothrium sb, antiaxial view; 331, female, right chela, antiaxial view; 332, female, detail of fingers at the chelal tip, antiaxial view; 333, female, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 334, female, detail of fingers at level of trichobothrium sb, antiaxial view.

FIGURES 410–413. Distribution maps for the Italian species of the Chthonius ischnocheles group. 410, Chthonius caoduroi Callaini, 1987, Chthonius gallettii n. sp., Chthonius inguscioi n. sp., Chthonius marciai n. sp. and Chthonius multidentatus Beier, 1963; 411, Chthonius caprai Gardini, 1977, Chthonius jonicus Beier, 1931 and Chthonius leoi (Callaini, 1988); 412, Chthonius halberti Kew, 1916, Chthonius nicolosii n. sp., Chthonius ressli Beier, 1956 and Chthonius stammeri Beier, 1942; 413, Chthonius horridus Beier, 1934, Chthonius italicus Beier, 1930 and Chthonius lanai n. sp.