Atractides (s. str.) lunipes Lundblad, 1956

Gerecke, Reinhard, 2021, The water mites of the family Hygrobatidae (Acari, Hydrachnidia) in Italy, Zootaxa 5009 (1), pp. 1-85 : 30-33

Atractides (s. str.) lunipes Lundblad, 1956

(Figs 15-16; 29 T; 32 E-F)

Material examined: Calabria: I 101, 0/1/0, slide; I 102, 4/12/0 (1/1/0 slide); I 1083, 4/0/0 (1/0/0 slide); Sicilia: All parts except for Madonie. I 61, 1/1/0 slide; I 109, 1/0/0 slide; I 133, 2/4/0 slide; I 165, 1/4/0 slide; I 178, 1/7/0 slide ;

I 563, 0/6/0 (0/1/0 slide); I 572, 0/3/0 (0/1/0 slide); I 1077 b, 0/3/0; I 1077 c, 0/2/0; I 1078 f, 0/2/0; I 1079 f, 0/6/0; I 1080 b, 0/1/0; I dp 138, 0/2/0. 16 sites, 74 specimens.

Fig. 15: Atractides lunipes ♂. A, I-L-5/6 (I 133); B, palp medial (I 61); C, venter (I 61, genital setae omitted); D, genital field (I 133). Scale bars: 100 µm.

Fig. 16: Atractides lunipes ♀ (I 133). A, I-L-5/6; B, genital field; C, palp medial; magnification as scale bar Fig. 15 C.

Remarks: As this species is still little documented (and the separation from A. corsicus is rather unclear, see below), selected specimens from Sicily are described here in detail.

Both sexes: Dorsal integument lineated. Glandularia small, round, diameter ca. 25; dorsocentral glandularia with distinctly elongated setae. Vgl-1+2 fused. Coxae without secondary sclerotization. I-L-5 (Figs 15 A, 16 A) ventral and dorsal margins equally diverging from base to S-1 insertion, between S-1 and -2 abruptly narrowed, with a strongly concave ventral margin in this part; S-1 long and slender, with a slight thickening in basal quarter, nearly parallel margins in the centre and equally narrowed distally, tip oblique truncated, forming a fine denticle on the inner side; S-2 distinctly shorter, maximum W in proximal third, tip bluntly pointed. Palp with strong sexual dimorphism; P-4 with maximum H near proximoventral seta.

Males (n = 3): Idiosoma L/W 480-550/370-410. Venter: Fig. 15 C. Coxal field L/W 280-330/310-360; Cx-I+II mL 100-110, lL 175-200, W 200-240. I-L-5 dL/vL 154-176/104-120, ratio 1.5, distoventral sector 19-27 %; HA 38-43, HB 43-48, HC 55-68, ratio dL/HB 3.6-3.7; S-1 L/W 78-98/6-8, ratio 12.4-13.0; S-2 L/W 65-68/8-9, ratio 7.7-8.7; distance S-1-2, 18-28, L ratio S-1/-2, 1.2-1.4; I-L-6 dL 116-132, HA 23, HB 15-18, HC 15-20; ratio dL/HB 7.1-7.7; dL ratio I-L-5/6, 1.24-1.34. Genital field (Fig. 15 D) L/W 78-92/84-100, rounded, anterior margin straight or very slightly concave, posterior margin with a shallow medial indentation that may be filled with secondary sclerite; gonopore L 50-55, Ac in a curved line, surrounded by about 25 pairs of setae (fine, hair like laterally, longer and stronger medially and at posteromedial edge); Ac relatively small, similar in size; maximum diameter Ac-1, 24- 28; Ac-2, 22-28; Ac-3, 24-32. Gnathosoma vL 100-108, chelicera L 176-186, L/H 5.2, basal segment/claw 2.2-2.4. Palp (Fig. 15 B) total L 255-280; L/H (ratio, rel. L [%]) P-1, 25-30/25-28 (1.0-1.1, 10-11); P-2, 60-68/55-73 (0.9- 1.1, 23-24); P-3, 55-58/40-45 (1.3-1.4, 21-22); P-4, 88-93/35-40 (2.3-2.5, 34-34); P-5, 28-33/10-11 (2.4-2.9, 11-12); L ratio P-2/P-3, 1.09-1.17, P-2/P-4, 0.69-0.73; P-3/P-4, 0.62-0.63. P-2 ventral margin proximally weakly concave, distally strongly protruding to form a bluntly pointed, digitiform extension directed anteroventrally; P-3 ventral and dorsal margins slightly diverging, ventral margin weakly concave, its distal third hyaline; P-4 shortened, dorsally with dense cover of fine, hair-like setae; ventral sectors nearly equal in L or central sector slightly longer; position of sword seta slightly distal from centre (ratio proximal/distal sector 1.1-1.2).

Females (n= 3): Idiosoma L/W 760-780/550-620, coxal field L/W 360-380/440-480; Cx-I+II mL 110-120, lL 220-230, W 340-360. I-L-5 dL/vL 220-232/136-140, ratio 1.6-1.7, distal sector 20-36 %; HA 48-53, HB 53-58, HC 85-88, ratio dL/HB 4.2-4.4; S-1 L/W 115-118/10, ratio 11.5-11.8; S-2 L/W 85-93/11-14, ratio 6.4-8.2; distance S-1-2, 43-45, L ratio S-1/-2, 1.2-1.4; I-L-6 dL 176-184, HA 20-24, HB 15-18, HC 18-20; ratio dL/HB 10.1-12.3; dL ratio I-L-5/6, 1.25-1.30. Genital field (Fig. 16 B) L 150-160, pre- and postgenital sclerites strong, genital plates L/W 104-1112/32-36, weakly curved, anteriorly bluntly pointed, posteriorly rounded, bearing 10-12 pairs of fine, hair-like setae; Ac similar in size, maximum diameter Ac-1, 30-36; Ac-2, 28-36; Ac-3, 30-36. Gnathosoma vL 112- 120, chelicera L 220-232, L/H 4.8-5.7, basal segment/claw 2.2-2.4. Palp (Fig. 16 C) slenderer than in male, total L 348-358; L/H (ratio, rel. L [%]) P-1, 30-33/30-33 (0.9-1.1, 9); P-2, 73-78/55 (1.3-1.4, 21-22); P-3, 93-98/40-43 (2.2-2.4, 27-28); P-4, 113-115/29-33 (3.5-4.0, 31-33); P-5, 35-40/10-13 (2.8-3.5, 10-11); L ratio P-2/P-3, 0.78-0.82; P-2/P-4, 0.63-0.69; P-3/P-4, 0.80-0.87. P-2 ventral margin in proximal part concave, distally strongly extending to form a rounded distoventral edge; P-3 ventral margin very weakly concave, in distal half hyaline, all over the segment subparallel to the weakly convex dorsal margin; P-4 distinctly slenderer than in males, dorsal setation less dense, ventral setae more away from each other and distoventral setae closer to distal segment edge (ventral sectors: 28-35, 46-53, 19-23).

The male of this species was unknown for several decennia, and also the first records of A. lunipes males from Corsica ( Gerecke & Di Sabatino 2013, Gerecke 2014b) were given without discussing morphological details. Material from Iran on which, with a question mark, a tentative first description of A. lunipes males had been based ( Pešić et al. 2004), was later assigned to a new species, A. zagrosensis Pešić, Saboori & Asadi, 2016 . In the same paper, the first description of the true male of A. lunipes was provided, based on material from Ardéche in France ( Pešić et al. 2016). Six measured specimens from Sicilian populations agree with the interpretation given there in the relatively low dL ratio I-L-5/6 (1.1-1.3), and males are also characteristic in a relatively slender I-L-6. However, proportions of female I-L-6 and of setae S-1/- 2 in both sexes grade into the variability of A. zagrosensis . The new data show furthermore that there is a wide overlap in most measurements and proportions between A.lunipes , and A. corsicus from Corsica and Sardinia. At present state of documentation, the following details remain for distinguishing A. corsicus from A. lunipes : Males have a more slender P-4 (L/H 2.5-2.8) and higher measurement values of I-L-5 HA (44-49), HB (48-56), and S-2 L (68-81); females differ in P-4, with a higher distance between distoventral seta insertion and distal end of ventral margin (23-28, 26-30 % ventral L), and I-L-5/6, with higher values of I-L-5 HA (58-63), HB (60-69), HC (100-118), S-1 L and L/W ratio (130-145, 12.8-16.3), distance S-1-2 (48-58), and I-L-6 L (188-225). Most of these features concern absolute measurement values, and/or regard one of the two sexes only. They are obviously weak for species discrimination, but I consider them strong enough to keep A. corsicus as a separate insular sister species of A. lunipes . The diagnostic differences proposed by Gerecke (2014b) with regard to the shape of S-1/-2 and I-L-6 do not allow to separate the two species - all records of A. lunipes from Corsica refer to A. corsicus (see there).

Habitat: Rhithrobiont. Middle order streams at various elevations, 2-930 m, scattered.

Distribution: Central-Western Mediterranean. First records from Italy.