Atractides (s. str.) remotus Szalay, 1953

Gerecke, Reinhard, 2021, The water mites of the family Hygrobatidae (Acari, Hydrachnidia) in Italy, Zootaxa 5009 (1), pp. 1-85 : 39-41

Atractides (s. str.) remotus Szalay, 1953

(Figs 19-20; 29 N-O; 32 C)

Material examined: Basilicata: I 427, 0/1/0 slide; I 1090, 1/0/0 slide; I 1093, 0/1/0 slide; I 1097, 0/1/2 slide; I 1123, 0/2/0 (0/1/0 slide); Calabria: I 106, 1/0/0 slide; I 412, 1/0/0 slide; I 422, 1/4/0 (1/1/0 slide); I 426, 1/0/0 slide; I 429, 1/1/0 slide; I 1101, 2/4/0 (1/1/0 slide); I 1102, 1/3/0 (1/1/0 slide); I 1105, 7/4/4 (2/2/0 slide); I 1111, 1/1/0 slide; I 1112, 0/1/0 slide; I 1115 b, 2/15/0, 2/3/0 slide; I 1116, 0/1/0 slide; I 1132, 0/1/0 slide; I 1231, 4/4/5 (1/1/0 slide); I TG 18-02b, 2/7/1; I TG 18-03b, 2/4/0; I TG 18-08a, 2/8/1; Friuli-Venezia Giulia: I Dor 2 riffle 27.09.2016, 0/1/0; I Dor 3 riffle 28.09.2016, 0/2/0; I Dor 5 riffle 19.12.2016, 0/2/0, 27.06.2017, 0/1/0; I Dor 5 pool 19.12.2016, 0/1/0; Lazio: I 881, 5/5/1 (1/1/1 slide); I 884, 2/18/0 (1/2/0 slide); I 1287, 0/1/1 slide; I 1288, 0/1/0 slide; Sicilia: Northeastern mountains ; I 249, 0/2/0 (0/1/0 slide); I 403, 0/2/0 (0/1/0 slide); I 502, 4/1/0 slide; I 599, 0/1/0 slide; I 627, 2/7/0 slide; I 628, 0/1/0 slide; I 647, 0/2/0 slide; I 649, 0/1/0 slide. 34 sites, 164 specimens .

Description: Integument strongly lineated; lateral eyes well developed and pigmented; dorsal and posteroventral muscle insertions, as well as anal pore, smooth; glandularia not enlarged, diameter about 25. Venter: Fig. 19 C. Vgl-1+2 separate from each other by an extended membranous area. Coxal plates in three groups, individual coxae (antero)laterally not distinctly projecting, together forming a smoothly undulating outline of the coxal field. Posterior margin of Cx-I+II equally convex, posterior apodemes of Cx-I stout and curved. I-L-5 dorsal and ventral margins straight, slightly diverging from base to insertion of S-1; S-1 equally narrowed from base to tip, but apically truncated, adaxial margin generally straight, only in basal sector slightly concave, at distal edge ending in a very fine extension; S-2 stout, in distal part equally narrowed, with a rounded tip. I-L-6 stout, curved, in basal part distinctly thicker than distally. Genital field with Ac in triangular arrangement (Figs 19 D, 20A). Gnathosoma with a short rostrum, chelicera L/H 4.9-6.0, basal segment/claw ratio 2.3-2.7. Palp with strong sexual dimorphism, P-4 maximum H on the level of proximoventral seta.

Males (n = 10): Idiosoma L/W 500-650/380-520; coxal field L/Cx-III W 290-360/325-440, Cx-I+II mL 110- 140, lL 180-240, W 270-310 (mL/W ratio 0.39-0,45). Coxal plates tending to fuse – in extreme cases completely melted forming a continuous coxal shield (Fig. 19 C). Genital field (Fig. 19 D) with equally rounded lateral and anterior margin – the latter broadly extending anterior to Ac-1, but with a deep posteromedial indentation (L/W 96-124/90-124, ratio 0.93-1.07), with 20-25 pairs of setae; Ac-1-3 maximum diameter 28-48, 24-44, 26-42, the extending anterior tips of Ac-3 close to posterior tips of Ac-1; gonopore L 55-65. I-L with segments 3 and 4 forming broadly protruding, rounded distal sheaths covering the base of the subsequent segments. I-L-5-6: Fig. 19 A. I-L- 5 dL/vL 168-204/108-140, ratio 1.39-1.56, ventral seta 19-32 % of vL away from S-1; HA 40-50, HB 48-58, HC 60-73, ratio dL/HB 3.3-3.8. L (L/W) S-1, 90-105 (9.3-14.9), S-2, 73-93 (6.4-8.7), distance S-1-2, 20-30, ratio S-1 L/distance S-1-2, 3.3-4.5. I-L-6 L 128-144, HA 24-29, HB 18-20, HC 16-21, ratio L/HB 6.6-8.0; ratio I-L-5 dL/I- L-6 L 1.25-1.42. Palp (Fig. 19 B) stout, total L 278-319; proportions of segments (L/H, ratio, % total L): P-1, 30- 35/25-30, 1.1-1.3, 10-12; P-2, 60-73/53-63, 1.08-1.30, 21-23; P-3, 63-74/40-25, 1.5-1.7, 22-23; P-4, 90-103/35-43, 2.3-2.6, 31-33; P-5, 33-38/11-14, 2.3-2.6, 11-13; L ratio P-2/P-3, 0.93-1.00, P-2/P-4, 0.65-0.74; P-3/P-4, 0.68-0.74. P-2 with a nose-shaped, often rugose distoventral projection; P-3 ventral margin slightly concave, in distal quarter with a short hyaline sector. P-4 very stout, with maximum H in distal quarter, both ventral setae in proximal half, sword seta distally from distoventral seta, in the distal part of the segment (ratio distance to proximal/distal edge: 1.1-2.6); sectors of ventral margin between seta insertion short proximally (24-34 %), very short centrally (14-23 %), long distally (48-61 %).

Fig. 19: Atractides remotus ♂ (I 502). A, I-L-5/6; B, palp medial; C, venter (genital setae omitted); D, genital field. Scale bars: 100 µm.

Fig. 20: Atractides remotus ♀ (I 502). A, genital field; B, I-L-5/6; C, palp medial. Scale bar: 100 µm.

Females (n = 10): Idiosoma L/W 560-950/480-700; coxal field L/Cx-III W 340-440/380-540, Cx-I+II mL 120- 150, lL 230-270, W 290-370 (mL/W ratio 0.36-0.48). Genital field (Fig. 20 A) L 150-190, acetabular plates L/W 108-128/36-48, ratio 2.7-3.6); Ac-1-3 maximum diameter 34-46, 34-44, 26-44, pregenital sclerite large, crescentshaped. I-L-3/-4 not forming distal sheaths. I-L-5-6: Fig. 20 B. I-L-5 dL/vL 212-264/140-172, ratio 1.45-1.62, dorsal and ventral margins only weakly diverging from the base to S-1 insertion, ventral seta distance to distoventral edge 22 - 38 % vL; HA 55-68, HB 60-70, HC 78-98, ratio dL/HB 3.5-3.8. L (L/W) S-1, 110-133 (11.0-13.3), S-2, 90-108 (5.6-7.2), distance S-1-2, 26-43, ratio S-1 L/distance S-1-2, 3.0-4.2. I-L-6 L 156-200, HA 26-33, HB 15-20, HC 20- 23, ratio L/HB 8.0-12.0; ratio I-L-5 dL/ I-L-6 L 1.27-1.38. Palp (Fig. 20 C) slender, total L 343-390; proportions of segments (L/H, ratio, % total L): P-1, 33-38/29-35, 1.0-1.2, 9-10; P-2, 73-85/55-68, 1.3-1.4, 21-22; P-3, 90-108/39- 51, 1.9-2.4, 26-28; P-4, 105-120/30-35, 3.2-4.0, 30-33; P-5, 38-40/11-15, 2.7-3.3, 10-11; L ratio P-2/P-3, 0.78-0.84, P-2/P-4, 0.65-0.74; P-3/P-4, 0.79-0.90. P-2 ventral margin in distal part slightly protruding and rounded; P-3 ventral margin straight or very weakly concave. P-4 sword seta insertion: ratio distance to proximal/distal edge 1.3-2.3; ventral setae insertions dividing ventral margin into two shorter proximal (25-31 %) and distal (24-38 %) sectors flanking a larger central one (37-50 %).

Remarks: Up to now, A. remotus appeared to have a Central-Southeast European distribution. The records given here extend remarkably the distribution area of the species and allow an analysis of the variability of important characters. In most measurements, there is a good agreement between the specimens investigated and data from Central Europe. The only differences found in Central European specimens (in parentheses data from Gerecke 2003) regard the slenderer shape of the male palp (L/H P-2, 1.07, P-4, 1.96) and major female Ac (maximum diameter 55/55/53). Furthermore, in most of the females examined, the Ac are not arranged in a close triangle, but in a more or less curved line. The fusion of the male coxal plates is in most cases restricted to the lateral part of the suture Cx-II/III. Regarding the shape of the male palp, data from Central European specimens are probably not representative – especially P-4 is often atypically inflated in slide-mounted specimens ( Gerecke 2003). The further observed differences are interpreted as a result of geographic variability.

Females of A. cydonius are rather similar in large posterior Ac, I-L-5 not remarkably inflated, and I-L-6 relatively short, distally narrowed. They differ in stouter, but relatively longer setae S-1 (L/W about 10.0, L ratio S-1/-2, 1.4- 1.6).

Habitat: Rhithrobiont, crenophilous, in the area treated about 50 % of the records from forest springs, 115 to 1530 m.

Distribution: Central and Southern Europe. First records from Italy.