Atractides (s. str.) protendens K.O. Viets, 1955

Gerecke, Reinhard, 2021, The water mites of the family Hygrobatidae (Acari, Hydrachnidia) in Italy, Zootaxa 5009 (1), pp. 1-85 : 38-39

Atractides (s. str.) protendens K.O. Viets, 1955

(Figs 26 G-H)

Material examined: Abruzzo: I 1187, 0/2/0; Basilicata: I 1089, 6/2/0 (1/1/0 slide); I 1093, 0/2/0; I 1094, 1/1/0; I 1121, 1/0/0; I 1123, 3/1/0; Calabria: I 1085, 0/2/0 (0/1/0 slide); I 1088, 0/1/0; I 1100, 1/0/0; I 1108, 0/1/0; I 1110, 0/1/0; I 1114, 3/3/1; I 1126, 2/3/0; I 1134, 0/1/0; I 1135, 3/0/1; Lazio: I 883, 2/1/0 slide; I 887, 0/1/0 slide; Lombardia: I TG 13-02b, 0/3/0; Sardegna: I TG 15-02, 2/5/0; I TG 17-03a, 0/1/0; Sicilia: All parts. I 59, 0/1/0 slide; I 99, 2/1/0 slide; I 100, 0/2/0 (0/1/0 slide); I 176, 1/0/0 slide; I 212, 1/0/0 slide; I 234, 0/1/0 slide; I 142, 1/0/0 slide; I 242, 1/0/0 slide; I 243, 1/5/0, 1/2/0 slide; I 244, 0/1/0 slide; I 250, 2/2/0 (1/1/0 slide); I 282, 0/2/0 (0/1/0 slide); I 286, 3/4/0 (2/2/0 slide); I 319, 0/1/0 slide; I 399, 0/2/0; I 401, 0/1/0 (0/1/0 slide); I 406, 2/5/0 (1/1/0 slide); I 407, 0/2/0 (0/1/0 slide); I 468, 1/1/1 slide; I 500, 2/0/0 slide; I 501, 1/1/0 slide; I 502, 3/1/0 slide; I 505, 1/0/0 slide; I 506, 0/2/0 (0/1/0 slide); I 517, 0/4/0 (0/1/0 slide); I 519, 0/1/0 slide; I 520, 2/5/0 (1/1/0 slide); I 529, 0/1/0 slide; I 553 Int, 1/0/0 slide; I 557, 1/1/0; I 559 Int, 0/0/1; I 560, 1/7/0; I 568, 0/2/0 (0/1/0 slide); I 575, 1/3/0 (1/1/0 slide); I 587, 2/0/0 slide; I 594, 4/3/0; I 596, 3/8/0 (1/1/0 slide); I 603, 3/3/0; I 604, 1/1/0 slide; I 607, 2/2/0; I 611, 1/0/0 slide; I 615, 1/0/0 slide; I 619, 1/0/0 slide; I 628, 1/0/0 slide; I 642, 2/4/1 (0/1/1 slide); I 647, 0/3/0 slide; I 649, 0/1/0 slide; I 650, 0/4/0; I 651, 0/1/0; I 657, 2/3/0; 659, 2/1/1; I 848, 0/1/0; I 1067, 1/0/0 slide; I 1068, 1/0/0 slide; I dp 12, 0/1/0 slide; I dp 56, 1/1/0 slide; I dp 64, 1/0/0 slide; I dp 66, 0/1/0 slide; I dp 67, 2/10/1 slide. 76 sites, 232 specimens.

Previously published records from Italy: Sardegna ( Gerecke 2014b); Trentino-Alto Adige ( Gerecke et al. 2009).

Description: Both sexes: Integument strongly lineated. Glandularia medium sized, in aged specimens glandularia enlarged and with slightly irregular outline, and coxae with secondary sclerotization. I-L-5-6: Fig. 26 G. I-L-5 slender, ventral and dorsal margins in proximal half slightly, in distal half more strongly diverging; S-1 and -2 rather short, little away from each other, similar in size with blunt tips; I-L-6 stout and little curved, maximum H in distal part, ventral margin slightly convex in proximal quarter, slightly concave at basal third, more distally again slightly convex; I-L-claws strong. Palp (Fig. 26 H) without remarkable sexual dimorphism, P-2 ventral margin slightly concave, forming a distoventral angle; P-3 and -4 slender, P-4 with maximum H near proximoventral seta, sword seta closer to distoventral seta insertions, both setae associated with a tiny pointed projection, ventral sectors similar in size, the distal one in general slightly longer than the others.

Males (n = 11): Idiosoma L/W 400-650/300-500, coxal field L/W 240-370/320-380; Cx-I+II mL 100-140, lL 185-240, W 240-300. I-L-5 dL/vL 132-156/86-112, ratio 1.3-1.5, distal sector 28-46 %; HA 28-33, HB 33-40, HC 45-53, ratio dL/HB 3.6-4.1; S-1 L 53-63, L/W ratio 9,6-12,5; S-2 L 48-60, L/W ratio 7.0-9.0; distance S-1-2, 6-8, L ratio S-1/-2, 1.0-1.2; I-L-6 dL 108-128, HA 25-29, HB 24-28, HC 31-36; ratio dL/HB 4.2-4.9, dL/HC 3.3-3.7; dL ratio I-L-5/6, 1.10-1.26. Genital field L/W 88-128/96-142, rounded, anterior margin in juveniles equally convex, in aged specimens medially strongly extended by secondary sclerotization, posterior margin with a shallow medial indentation; gonopore L 50-65, Ac in a curved line, surrounded by 16-18 pairs of setae; maximum diameter Ac-1, 24-34; Ac-2, 22-32; Ac-3, 24-32. Gnathosoma L 116-148, chelicera L 204-244, L/H ratio 4.8-5.4, basal segment/ claw 2.2-2.4. Palp total L 254-308; L/H (ratio, rel. L [%]) P-1, 25-30/21-28 (1.0-1.2, 9-10); P-2, 56-65/40-50 (1.3- 1.5, 21-24); P-3, 60-75/33-40 (1.7-2.0, 23-25); P-4, 83-108/28-35 (2.9-3.1, 32-36); P-5, 25-30/10-14 (2.2-2.7, 9-11); L ratio P-2/P-3, 0.85-1.02; P-2/P-4, 0.58-0.74; P-3/P-4, 0.67-0.73.

Females (n = 3): Idiosoma L/W 580-750/480-600, coxal field L/W 350-380/420-510; Cx-I+II mL 130-140, lL 260-300, W 340-370. I-L-5 dL/vL 188-196/132-144, ratio 1.4-1.7, distal sector 33-36 %; HA 43-45, HB 50-53, HC 66-69, ratio dL/HB 3.7-3.8; S-1 L 74-80, L/W ratio 9.4-11.4; S-2 L 65-73, L/W ratio 6.5-7.3; distance S-1-2, 13-15, L ratio S-1/-2, 1.1-1.2; I-L-6 dL 156-164, HA 33-35, HB 30-34, HC 43; ratio dL/HB 4.9-5.3, dL/HC 3.7-3.9; dL ratio I-L-5/6, 1.20-1.21. Genital field L 130-180, pregenital sclerites crescent-shaped, with fine tips, Postgenital sclerite half disk shaped, with straight anterior margin, genital plates L/W 124-132/44-48, weakly curved, anteriorly forming a blunt tip, posteriorly rounded, bearing 10-12 pairs of fine, hair-like setae; Ac similar in size, maximum diameter Ac-1, 44; Ac-2, 38-46; Ac-3, 38-42. Gnathosoma L 180-184, chelicera L 320-328, L/H ratio 5.5-5.7, basal segment/claw 2.3. Palp total L 359-378; L/H (ratio, rel. L [%]) P-1, 35-38/30-33 (1.2, 10); P-2, 78-85/60-63 (1.3- 1.4, 22-23); P-3, 95-100/48-50 (2.0, 26); P-4, 115-118/33-35 (3.4-3.5, 31-32); P-5, 36-38/14-15 (2.5-2.6, 10); L ratio P-2/P-3, 0.82-0.85; P-2/P-4, 0.67-0.72; P-3/P-4, 0.83-0.85. P-2 and P-3 with straight ventral margins, P-4 slenderer than in males, fine dorsal setae less numerous.

Remarks: At a first glance, specimens of A. protendens resemble A. graecus . Occasionally, a key difference, the lineation of the dorsal integument (in A. graecus finely striated as the palm of a human finger), is to be seen with difficulty only in undissected specimens or after treatment with chemical agents (e.g., after enzymatical digestion). The new measurements show that A. protendens can be distinguished from A. graecus (in parentheses) also by generally larger acetabula - maximum diameter ♂♂ 22-32 (16-21), ♀♀ 38-46 (19-28), and several details of the I-L, e.g. I-L-5 longer, but stouter, ♂♂ dL> 130 (<125), ♀♀> 180 (<160), in both sexes dL/HB ratio 3.6-4.1 (4.1-4.5), setae S-1/-2 longer,> 45 (<45) and more away from each other, distance 8-14 (3-4). At site I 647, both species were found coexisting.

Habitat. Crenobiont – more than 80 % of the records in the study area from springs, mostly weakly seeping rheohelocrenes. In exceptional cases in low order streams, in two occasions taken in interstitial digs. Most records from middle to higher elevations (mean 930, maximum 1800 m), but also in the macchia belt (minimum 150 m).

Distribution: Central and Southern Europe. The numerous new records suggest that A. protendens is a typical Mediterranean species that has extended its northern distribution margin under favourable conditions (sun-exposed open land springs) to the Alps and scattered parts of central European mountain ranges.