Chthonius ressli Beier, 1956

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 : 116-120

Chthonius ressli Beier, 1956

( Figs 373–386 , 412 )

Chthonius (C.) ressli Beier, 1956: 24 , fig. 1.

Chthonius (C.) parvulus Inzaghi, 1981: 67 , figs 1–11 (synonymized by Judson 1990: 599).

Chthonius (C.) ressli: Judson 1990: 599 , figs 4–9; De Vore-Scribante 1999: 12, figs 7a–e; Novák & Kutasi 2014: 190, figs 1–3.

Type locality: Austria, Niederösterreich, Purgstall an der Erlauf, Bahnhofgelände [Railway Station area] (48°03’27”N, 15°08’24”E) .

Distribution. Czech Republic, Slovakia, Austria, Hungary, Switzerland, France, Italy.

Diagnosis (♂ ♀). An eyed epigean 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 of carapace with 4 macrosetae, the lateral macrosetae shorter than the median ones; chelicerae without lateral microsetae; chela length 0.45–0.62 mm; movable chelal finger length 0.30–0.41 mm; fixed chelal finger with 13–16 distal contiguous teeth, middle part of fixed finger with reclined, pointed, widely spaced teeth; ratio of pedipalpal femur/carapace 1.05–1.25.

Material examined. ITALY — Liguria: Genoa Prov. — 1 ♀, Genoa, Botanical Garden University , 15.II.2016, A. Pes & M. Zinni leg. ; 3 ♂ 1 ♀, Genova, Pegli, Torre Cambiaso , 17.IX.1978, G. Gardini leg. , sieved under Quercus ilex ; 3 ♀, Genova, Righi , V.2012, L. Galli leg. , Quercus ilex wood; 1 ♀, Genova, San Martino , VII.2007, L. Galantini leg .; 1 ♂ 2 ♀ 2 T, Genova, Sant’Ilario, Istituto Marsano , 30.X.2009, A. Comenale & G. Gardini leg. , hollow in Olea ; 1 ♀, id., 3.XII.2009, A. Comenale & G. Gardini leg., hollow in Olea ; 1 ♂ 2 ♀, Genova, Villetta Di Negro , 21. V.1972, G. Gardini leg. , sieved under Quercus ilex ; 1 ♀, id., 4. VI.1972, G. Bartoli leg.; 1 T, id., 8.X.1972, G. Bartoli leg .; 1 ♀, id., 1. V.1975, R. Poggi leg. , sieved under Quercus ilex ; 1 ♀, id., IX.1979, S. Vit leg. Liguria: La Spezia Prov. — 2 ♂ 4 ♀, Ceparana, bed of Fiume Magra , 26.IV.2002, G. Gardini leg. Emilia: Bologna Prov. — 10 ♂ 22 ♀, Gaibola near Bologna , 8.XII.1983, C. Torti & S. Zoia leg. , mixed wood with Castanea . Latium: Rome Prov. — 1 ♂ 1 ♀, Rome, Monte Mario , 18. VI.1991, L. Latella leg.

SWITZERLAND — Geneva — 1 ♂ , Geneva, Versoix , 17.XI.1995, S. Vit leg., rotten strain; 3 ♂ 8 ♀ 4 T, id., 25.XI.1995, S. Vit leg., under Taxus .

Description of adults (♂ ♀). Integument slightly pigmented, carapace, tergites, chelicerae and pedipalps pale brown; weak hispid granulation on anterolateral surfaces of carapace and on cheliceral palm. Carapace ( Fig. 375 ) almost square, 0.9–1.1 times longer than broad; anterior margin between median macrosetae with prominent epistome in both sexes ( Figs 373–374 ); ocular area as in fig. 375, anterior eyes strongly reduced, posterior ones as vestigial remains, but all eyes with a weak tapetum; standard chaetotaxy 4:6:4:2:4(20), rarely anterior row with 5, ocular row with 7, posterior row with 3 macrosetae; lateral setae of posterior row shorter than the median ones; length of anteromedian macrosetae 0.06–0.08 mm. Chaetotaxy of tergites 4:4:4:4:6:6:6:6:1T2T1:4:1T2T1:0. Standard chaetotaxy of sternites II–X: 9:(3)7–11(3):(2)7–8(2):8–9:6:6:6:6:2T1T2; genital opening of males flanked by 6–7 (rarely 5) setae on each side. Chelicerae ( Fig. 376 ) 1.95–2.25 (♂ ♀) times as long as broad, palm with 6 setae, without lateral microsetae; fixed finger with 7–14 (mainly 10–11) teeth and few proximal microtubercles; movable finger with an isolated subapical tooth (di) at level with the spinneret, and 6–12 (mainly 9–11) teeth proximally reduced in size; gs ratio 0.54–0.60; spinneret weakly prominent, rounded and similar in both sexes ( Figs 376–377 ); rallum with 11 blades; serrulae interior and exterior with 11–13 and 13–15 blades respectively. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 3 + 3 marginal microsetae, II 4, III 6, IV 7 (coxa III rarely with 4 or 5, coxa IV rarely with 6 setae); coxa II with 6–10 coxal spines, coxa III with 2–5 coxal spines; intercoxal tubercle bisetose. Pedipalp: femur 4.25–4.9 (♂) or 4.3–4.8 (♀) times as long as broad, femoral chaetotaxy 3:6:2:5:1; chela ( Figs 380, 383 ) 4.7–5.5 (♂) or 4.3–5.0 (♀) times as long as deep; hand of chela 1.5–1.7 (♂ ♀) times as long as deep, ovoid outline in dorsal view ( Figs 378–379 ); fixed chelal finger with 34–53 teeth that are inclined backwards: 13–16 distal teeth contiguous, pointed and small; 6–12 large, sharp, reclined and widely spaced teeth; 15–22 proximal teeth low, more contiguous, rounded, and reduced in size towards finger base ( Figs 381–382, 384– 386 ); all teeth with dental canal; fixed finger at level of est-it with 8–11 teeth occupying 0.1 mm, distance between successive apices 0.009 –0.017 mm; tip of fixed chelal finger with apical sensilla af 1- 2, distal paraxial seta gradually curved and thin; movable chelal finger with 31–42 teeth, slightly scalene triangle-shaped, reclined and apically pointed proximally up to trichobothria t -st, rounded and increasingly reduced from st towards finger base, reaching back near b (between sb and b they are mainly recognizable only by the presence of dental canal) ( Figs 381–382, 384–386 ); movable finger at level of st-t with 9–12 teeth occupying 0.1 mm, distance between successive apices 0.008 –0.011 mm; coupled sensilla pc just distad of sb, positioned on a weak tubercle; tip of movable chelal finger with apical sensilla am 1- 2; trichobothria as in figs 380, 383; ratio sb -st/sb -b = 1.4–1.7; ratio of movable finger/hand of chela 1.8–2.2 (♂ ♀); ratio of pedipalpal femur/movable finger 0.95–1.0 (♂ ♀); ratio of pedipalpal femur/carapace 1.05–1.25 (♂ ♀).

Measurements (in mm). Body length 0.85–1.0 (♂) or 1.0–1.3 (♀). Carapace 0.25–0.33 × 0.27–0.31 (♂) or 0.29–0.39 × 0.30–0.41 (♀). Chelicerae 0.24–0.28 × 0.11–0.14 (♂) or 0.29–0.35 × 0.14–0.18 (♀); movable finger length 0.12–0.155 (♂) or 0.15–0.18 (♀). Pedipalp: femur 0.295 –0.355 × 0.06–0.08 (♂) or 0.34–0.44 × 0.075–0.09 (♀); chela 0.45–0.535 × 0.09–0.11 (♂) or 0.53–0.62 × 0.11–0.135 (♀); hand length 0.15–0.175 (♂) or 0.175 –0.205 (♀); movable finger length 0.30–0.36 (♂) or 0.34–0.41 (♀).

Description of tritonymph. Integument with weak pigmentation, hispid granulation less marked than in adults. Carapace 0.90–1.0 times longer than broad, form of anterior margin and eyes as in adults; chaetotaxy 4:6:4:2:4(20); length of anteromedian macrosetae 0.050 –0.055 mm. Chaetotaxy of tergites as in adults. Chaetotaxy of sternites II–IX 5:(2)8(2):(1)6(1):6–8:6:6:6:6. Chelicerae 1.9–2.1 times as long as broad, palm with 5 setae and without lateral microsetae; fixed finger with 8–11 teeth, proximally reduced in size; movable finger with an isolated subapical tooth (di) and 7–9 teeth; gs ratio 0.55–0.60; spinneret prominent and apically rounded as in females; rallum with 9 blades; serrulae interior and exterior with 10 and 11–12 blades respectively. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 3 + 2 marginal microsetae, II 4, III 4, IV 5; coxa II with 5–8 coxal spines, coxa III with 2–3 coxal spines; intercoxal tubercle bisetose. Pedipalp: femur 3.9–4.5 times as long as broad; chela 4.2–4.7 times as long as deep; hand of chela 1.45–1.7 times as long as deep; fixed chelal finger with 38–44 teeth, all with dental canal; movable chelal finger with 28–34 teeth, reduced in size towards finger base; coupled sensilla pc nearer to b than to st or halfway between b-st, on a weak tubercle; ratio of movable finger/hand of chela 1.8–1.9; ratio of pedipalpal femur/movable finger 0.9–1.0; ratio of pedipalpal femur/carapace 0.9–1.05.

Measurements (in mm). Body length 0.7–0.9. Carapace 0.23–0.275 × 0.23–0.265. Chelicerae 0.20–0.23 × 0.095–0.12, movable finger length 0.095 –0.115. Pedipalp: femur 0.23–0.25 × 0.055 –0.065; chela 0.37–0.41 × 0.08–0.10; hand length 0.13–0.14; movable finger length 0.245–0.27.

Remarks. Chthonius ressli does not closely resemble any of the Italian species of the C. ischnocheles group, due its distinctive pattern of finger chelal teeth. The only species with a similar dentition pattern is C. hungaricus Mahnert, 1981 from Hungary, Romania and Slovakia ( Mahnert 1981; Christophoryová, Fenďa & Krištofík 2011; Gardini 2014). Chthonius ressli differs from C. hungaricus in the following main characters: anterior eyes usually reduced and posterior eyes as vestigial remains (anterior eyes with convex lens and posterior eyes with flat lens in C. hungaricus ); anterior margin of carapace without preocular microsetae (with 1 microseta on each side in C. hungaricus ); posterior margin of carapace with 4 macrosetae (with 2 macrosetae in C. hungaricus ); chelicerae without lateral microsetae (with 1 lateral microseta in C. hungaricus ); chela length 0.45–0.535 (♂) or 0.53–0.62 (♀) mm [0.65–0.66 (♂) or 0.71–0.73 (♀) mm in C. hungaricus ]; movable chelal finger length 0.30–0.36 (♂) or 0.34–0.41 (♀) mm [0.44–0.47 (♂), 0.48–0.49 (♀) mm in C. hungaricus ].

The above description of Chthonius ressli partially incorporates those by Inzaghi (1981), Judson (1990) and De Vore-Scribante (1999).

Figures

FIGURES 373–379. Chthonius ressli Beier, 1956, Gaibola near Bologna. 373, male, anterior margin of carapace; 374, female, id.; 375, male, carapace; 376, male, right chelicera; 377, female, movable finger of right chelicera; 378, male, right chelal hand, dorsal view; 379, female, id.

FIGURES 380–386. Chthonius ressli Beier, 1956, Gaibola near Bologna. 380, male, right chela, antiaxial view; 381, male, detail of fingers at the distal half of chela, antiaxial view; 382, male, detail of fingers at level of trichobothrium sb, antiaxial view; 383, female, right chela, antiaxial view; 384, female, detail of fingers at the chelal tip, antiaxial view; 385, female, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 386, 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.