Atractides circumcinctus Schwoerbel, 1956

Gerecke, Reinhard, 2017, Rediscovery of the water mite Atractides circumcinctus Schwoerbel, 1956 (Acari: Hydrachnidia) in the Black Forest National Park, Acarologia 57 (3), pp. 665-671 : 666-669

Atractides circumcinctus Schwoerbel, 1956

Material examined — Black Forest National Park, Schönmünzach valley: Site D 804, S Grossbrunnen, spring at lower forest road, 710 m, 8°17’46.38"E, 48°34’5.69"N; 01.07.2015, eucrenal, 2 ♀♀, slidemounted; 25.08.2016, eucrenal, 6 ♂♂, 7 ♀♀, 2 deutonymphs (4 ♂♂, 4 ♀♀, 3 deutonymphs slidemounted, 2 ♂♂, 3 ♀♀ in ethanol); hypocrenal, 1 ♀, in ethanol. Site D 821, spring of upper affluent to Stumpenteich stream, 740 m, 8°19’44.97"E, 48°34’32.55"N; 25.09.2015, eucrenal, 1 ♀, slidemounted.

Senckenberg, collection Schwoerbel:

Holotype ♂, " Hydrachnellae 457 Pionae Atractidae Atractides ; A. circumcinctus TYPUS ♂ ADA6– Quelle am Schauinsland, 1000 m, 27"; "Sauterquelle Feldberg/Schw., Okt., 1960", 1 ♂; "Schwarzwald 1077", 1 ♂; "Hydrachnellae 294 Pionae Atractidae Atractides ; A. circumcinctus P.Typus ♀. Bohrerbach, Oberlauf, in Moosen Freiburg, Jan, 1954", 1 ♀; "Quelltümpel Haslachtal 20.3.1957, 1174", 1 ♀; "Schwarzwald 1081", 4 ♀♀ on one slide; "Schwarzwald 1067", 1 ♀; three slides without locality information, marked "paratypoid", numbered "786", "797", "801", each bearing 1 ♀.

Redescription — Both sexes: Colour of sclerotized parts greyish brown, idiosoma with extended red areas. Integument with a very fine striation, dorsal and posteroventral muscle insertions unsclerotized, glandularia small, round (maximum diameter of Dgl-3, 20-23), setae of Dgl-1,-3, and -4, and Lgl-2 very long, all others short (Fig. 1G); coxal field with strong sexual dimorphism; apodemes of Cx-II directed laterally; Legs without sexual dimorphism, claws with claw blade and ventral clawlet; I-L-5/6: Figs 1B-D; I-L-5 extremely elongate, in the centre slightly narrowed and here with a ventral seta barely differing from the surrounding ones, dorsal and ventral margin diverging only towards distal segment end; setae S-1 and -2 close to each other (separation <maximum W S-2), rather stout and apically rounded; S-1 slightly shorter and more slender than S-2; I-L-6 (Fig. 1D) strongly shortened and curved, equally narrowed from base to tip. Genital field with subtriangular acetabula in a weakly curved line. Excretory pore smooth, Vgl- 1/2 generally separate, but often very close (Fig. 1A, arrow), occasionally fused. Gnathosoma without particularly projecting rostrum, palp with slight sexual dimorphism in proportions; P-2 ventral margin without extensions, weakly concave in basal part, distally forming an obtuse angle; P-4 maximum H

FIGURE 1: Atractides circumcinctus ♂ (D 804). A – venter (arrow: Vgl-1/2); B – I-L-5/6, antiaxial view; C – I-L-5/6, paraxial view (detail 667: setae S-1, S-2); D – I-L-6; E – palp, paraxial view; F – palp, antiaxial view; G – dorsum. Scale bars: 100 µm.

Gerecke R.

near proximoventral seta, sword seta insertion between ventral seta insertions, in centre of segment or slightly shifted to distal part; sectors between ventral setae nearly equal in length or distal sector slightly shortened.

Males (n = 4; palp and I-L, n = 3; gnathosoma and chelicera, n = 1) — Idiosoma L/W 440-510/240- 400, venter: Fig. 1A; coxal field L/W 270-290/350- 360, fused to form an extended shield including also Vgl-3 and V-1 (visible as a finely dotted area); posterior margin of coxal shield medially deeply indented, in lateral parts equally rounded; Cx-I+II mL 105-130, lL 184-210, W 233-250. I-L-5/6: Fig. 1C; I-L- 5 dL/vL 141-146/123-124, ratio 1.15-1.19; HA 29-32, HB 38-40, HC 40-41, ratio dL/HB 3.53-3.76; S-1 L/W 50-53/7-8, ratio 6.5-7.6; S-2 L/W 55-56/9-11, 5.1-6.1; separation S-1-2, 6-7, L ratio S-1/-2, 0.91-0.95; I-L- 6 dL 75-77, HA 25-26, HB 18, HC 16; ratio dL/HB 4.2-4.4; dL ratio I-L-5/6, 1.8-1.9. Genital field as long as wide, L/W 106-112/110-116, anterior margin with projecting border of secondary sclerotization, posterior margin indented, gonopore L 45-54, flanked by a line of 7-8 fine setae, 3-5 further setae scattered at the lateral and posterior plate margins; maximum diameter Ac-1, 29-34; Ac-2, 31-39; Ac-3, 29-30. Gnathosoma L 80; chelicera L/H 148/31 (ratio 4.8), L ratio basal segment/claw 2.3. Palp: Figs 1E-F; total L 242-255; L/H (ratio, rel. L [%]) P-1, 25- 26/20-21 (1.2-1.3, 10-11); P-2, 52-55/38-39 (1.4, 21- 22); P-3, 52-53/30-34 (1.6-1.7, 21); P-4, 88-94/30-33 (2.9, 36-37); P-5, 24-27/10-11 (2.4-2.5, 10-11); L ratio P-2/P-3, 1.00-1.04; P-2/P-4, 0.59-0.60; P-3/P-4, 0.56- 0.59; P-4 with dense cover of fine, hair-like setae.

Females (n = 7, gnathosoma and chelicera n = 1) — Idiosoma L/W 560-630/380-500, venter: Fig. 2A ; coxal field L/W 250-305/370-420, coxae in 3 groups, with a narrow border of secondary sclerotization, posteromedial margin of Cx-I+II broadly rounded, posterior margin of Cx-IV weakly convex to nearly straight, perpendicular to the longitudinal axis; Cx- I+II mL 110-120, lL 195-225, W 240-274. I-L-5 dL/vL 168-181/139-161, ratio 1.1-1.2; HA 35-40, HB 44-46, HC 45-47, ratio dL/HB 3.7-4.0; S-1 L/W 55-61/6- 8, ratio 7.4-10.2; S-2 L/W 59-63/10-12, ratio 5.0-6.1; separation S-1-2, 6-7, L ratio S-1/-2, 0.93-1.03; I-L- 6 dL 77-86, HA 25-29, HB 18-21, HC 16-17; ratio dL/HB 4.1-4.5; dL ratio I-L-5/6, 2.02-2.35. Genital field L/W 162-193/180-210, pre- and postgenital sclerites strong, genital plates L/W 100-120/38- 49, weakly curved, anteriorly pointed, posteriorly rounded, bearing about 10 pairs of fine, hair-like setae; maximum diameter Ac-1, 36-45; Ac-2, 34-42; Ac- 3, 31-35. Gnathosoma L 108; chelicera L/H 177/38 (ratio 4.7), L ratio basal segment/claw 2.4. Palp: Fig. 2B ; total L 247-295; L/H (ratio, rel. L [%]) P- 1, 27-29/21-23 (1.2-1.4, 10-11); P-2, 53-66/32-41 (1.5- 1.7, 21-23); P-3, 56-71/29-35 (1.9-2.2, 23-24); P-4, 86- 99/27-30 (3.1-3.5, 33-35); P-5, 25-30/10-11 (2.5-3.0, 10-11); L ratio P-2/P-3, 0.90-0.98: P-2/P-4, 0.62-0.70; P-3/P-4, 0.65-0.72. As often in Atractides , female palp more slender than in males (L/H in males P- 2 <1.45, P-3 <1.9, P-4 <3.0), with a less dense cover of fine setae. Furthermore, P-3 relatively longer (in males, L ratio P-2/P-3 ≥ 1.0, P-3/P-4 <0.6).

Deutonymph (n= 3; palp: n = 1) — Idiosoma L/W 300-370/220-300, venter: Fig. 2C ; coxal field L/W 155-170/205-240, coxae in 3 groups, Cx-I+II mL 40-55, lL 100-115, W 145-160. I-L-5/6: Fig. 2E ; I-L-5 dL/vL 86-89/75-78, ratio 1.1; HA 23, HB 26-29, HC 27-29, ratio dL/HB 3.1-3.3; S-1 L/W 34-35/5-6, ratio 5.8-6.8; S-2 L/W 38-40/6-7, ratio 5.7-6.3; distance S-1-2, 3, L ratio S-1/-2, 0.9; I-L-6 dL 53-54, HA 21, HB 15, HC 12; ratio dL/HB 3.5-3.6; dL ratio I-L- 5/6, 1.6-1.7. Genital field L/W 45/66-67; maximum diameter Ac-1, 15-19; Ac-2, 18. Gnathosoma L 63-67; Palp: Fig. 2D ; total L 155; L/H (ratio, rel. L [%]) P-1, 16/12 (1.3, 10); P-2, 35/22 (1.6, 23); P-3, 33/18 (1.8, 21); P-4, 53/17 (3.1, 34); P-5, 18/8 (2.3, 12); L ratio P-2/P-3, 1.06: P-2/P-4, 0.66; P-3/P-4, 0.62. As typical for deutonymphs, many setae are reduced and the genital field bears only two pairs of Ac. Platelets Vgl-1/2 are distinctly separate in all specimens. Proportions of L-I-5/6 are less extreme than in adults, but I-L-6 is shortened and typical in shape.

Figures

FIGURE 2: Atractides circumcinctus (D 804); A – ♀ venter (arrow: Vgl-1/2); B – ♀ palp; C-F – deutonymph; C – venter (arrow: Vgl-1/2); D – palp; E – I-L-5/6. Scale bars: 100 µm.