Atractides (s. str.) cydonius, Gerecke, 2021

Gerecke, Reinhard, 2021, The water mites of the family Hygrobatidae (Acari, Hydrachnidia) in Italy, Zootaxa 5009 (1), pp. 1-85 : 16-18

Atractides (s. str.) cydonius sp. nov.

(Figs 8-9; 30 O; 32 N)

Type series: Holotype ♂, SMF, Calabria: I 1106 ( CS), Pollino, Morano Calabro, spring E Convento di Colloreto , 900 m, UTM WE 989 162, 05.10.1990, slide . Paratypes: ♀, same site and date as holotype, slide; Calabria: I 1101 a, 0/1/2; I 1107, 2/1/0 slide; I 1110, 1/3/1 (1/1/1 slide); I 1118, 1/5/0 (1/1/0 slide); I 1119, 0/3/0 (0/1/0 slide); I 1120, 1/3/1 (1/1/0 slide); I 1126, 2/1/0 slide; I 1127 b, 0/4/0 (0/1/0 slide); I TG 18-04b 2/0/1 (1/0/0 slide). 10 sites , 37 specimens.

Diagnosis: Integument lineated; dorsal and posteroventral muscle insertions not sclerotized. Genital field with Ac in a weakly curved line. Excretory pore without sclerotization, Vgl-1/-2 separate. I-L-5 moderately thickened, S-1/-2 robust, apically bluntly pointed, distanced (♂ 20-23, ♀ 30-38); I-L-6 curved, in basal third strongly narrowed (Figs 8 D, 9 D). Males: Genital field anteromedially protruding, posteriorly indented (Figs 8 A, 9 C); P-2 distoventral margin convexly protruding (Fig. 8 B-C). Females: Genital plates on level of Ac-3 large, anteriorly strongly narrowed (Fig. 9 B); P-2 distoventral margin less protruding than in male (Fig. 9 A).

Description: Integument around genital field striated, on lateral parts with stronger lines, on dorsal surface typically lineated; all muscle insertions unsclerotized, margins of coxae and genital field without secondary sclerotization; glandularia not enlarged (maximum diameter 25-30). Coxal plates in three groups. Genital field with 3 pairs of Ac, generally in a weakly curved line, occasionally, mostly in males, forming an obtuse angle, but Ac-3 always more distanced from Ac-1 than from Ac-2. Postgenital field with smooth excretory pore and unfused Vgl-1/- 2. I-L-5 ventral and dorsal margins distally slightly diverging; distance of setae S-1/-2 wider than the sum of their maximum W; seta S-1 with a central thickening, distally narrowed and with a blunt tip, seta S-2 distinctly thicker and shorter, apically blunt. I-L-6 curved, with maximum H near base, in basal third strongly narrowed. Palp with slight sexual dimorphism in shape of P-2; ventral margin of P-3 straight to very weakly concave; P-4 with ventral setae relatively short, more distanced from each other than from base resp. tip of segment, sword setae closer to distoventral seta. Females: P-2 distoventral margin less protruding than in male.

Fig. 8: Atractides cydonius sp. nov., type series ♂ (I 1106, 1120). A, venter; B, palp lateral; C, palp medial (P-1 missing); D, I-L-5/6. Scale bars: 100 µm.

Males (n = 2): Idiosoma L/W 530-550/400-450; coxal field L/Cx-III W 320/340-350, Cx-I+II mL 110, lL 210-215, W 260-280 (mL/W ratio 0.39-0,42). Genital plate (L /W 108-112/116, ratio 0.93-0.97), with 17-20 pairs of setae; in shape of a medially cut quince, anteromedially with a somewhat irregular, rounded or obtuse-angled projection covered by fine porosity (thus, part of primary sclerotization); posteromedial margin indented; Ac-1-3 maximum diameter 28-42, 24-44, 35-36, the extending anterior tips of Ac-3 more distanced from posterior tips of Ac-1 than from Ac-2 (in Fig. 9 C at right side an exceptional case with Ac nearly at equal distance); gonopore relatively short, L 60-65. I-L-5 dL/vL 172-180/112-116, ratio 1.54-1.55, ventral seta distance to distoventral edge 29-30 % of vL; HA 48, HB 53, HC 68, ratio dL/HB 3.3-3.4. L (L/W) S-1, 95 (9.5), S-2, 73-75 (5.8-6.7), distance S-1-2, 20-23, ratio S-1 L/distance S-1-2, 4.2-4.8. I-L-6 L 128-132, HA 28, HB 18-20, HC 20-23, ratio L/HB 6.6-7.3; ratio I-L-5 dL/I-L-6 L 1.34-1.36. Gnathosoma L 140-144; chelicera L 200-204, L/H 4.6-5.1, basal segment/claw 2.2-2.3. Palp total L 275-286; proportions of segments (L/H, ratio, % total L): P-1, 28-29/25, 1.1-1.2, 10; P-2, 63-65/46-48, 1.35-1.37, 23; P-3, 63/38, 1.7, 22-23; P-4, 93-98/33-35, 2.8-2.9, 34; P-5, 30-33/9-11, 2.7-3.7, 11; L ratio P-2/P-3, 1.00-1.04, P-2/P-4, 0.67-0.68; P-3/P-4, 0.64-0.68; distoventral margin of P-2 nose-shaped protruding, smooth; P-3 ventral margin slightly concave. P-4 with sword seta between ventral setae, closer to distoventral one (ratio distance to proximal/distal edge: 1.4-1.7); sectors of ventral margin between seta insertion short proximally (26-32 %), longest centrally (44-48 %), shortest distally (24-26 %).

Females (n = 2): Idiosoma L/W 600-850/500-700; coxal field L/Cx-III W 340-410/410-540, Cx-I+II mL 120- 130, lL 240-280, W 345-350 (mL/W ratio 0.35-0.37). Genital field L 210-270, acetabular plates L/W 128-132/48-52, ratio 2.5-2.7), Ac-1-3 maximum diameter 44-48, 40-42, 40-46, pregenital sclerite relatively small, crescent-shaped. I-L-5 dL/vL 236-248/160-192, ratio 1.23-1.55, ventral seta distance to distoventral edge 31-33 % vL; HA 60-66, HB 68-70, HC 90-98, ratio dL/HB 3.5. L (L/W) S-1, 125-130 (10.0), S-2, 83-90 (5.5-6.0), distance S-1-2, 30-38, ratio S-1 L/distance S-1-2, 3.3-4.3. I-L-6 L 176-184, HA 29-30, HB 19-20, HC 23-25, ratio L/HB 9.2-9.4; ratio I-L-5 dL/ I-L-6 L 1.34-1.35. Gnathosoma L 176-196; chelicera L 284-312, L/H 5.9-6.5, basal segment/claw 2.4- 2.6. Palp slenderer than in males, total L 363-385; proportions of segments (L/H, ratio, % total L): P-1, 35/30-33, 1.1-1.2, 9-10; P-2, 78-88/53-55, 1.5-1.6, 21-23; P-3, 95-100/43-44, 2.2-2.3, 26; P-4, 115-123/30-35, 3.5-3.8, 30-35; P-5, 40/14-15, 2.7-2.9, 10-11; L ratio P-2/P-3, 0.82-0.88, P-2/P-4, 0.67-0.71; P-3/P-4, 0.82-0.83. P-2 ventral margin straight, distal corner rounded; P-3 ventral margin straight; P-4 sword seta insertion: ratio distance to proximal/distal edge 1.2; ventral setae insertions dividing ventral margin into a short proximal (24-26 %) and distal (29-32 %) sectors flanking a larger central one (45 %).

Derivatio nominis: Many Atractides males have a genital plate shaped like a medially-cut apple, the one of A. cydonius resembles the surface of a bisected quince (lat.: malum cydonium).

Remarks: In the combination of a lineated integument, Ac in the genital field arranged in a weakly bowed curve, and the male palp without distoventral projection, A. cydonius is most similar to A. fluviatilis . It differs from the latter in both sexes in genital field shape and arrangement of Ac ( A. fluviatilis: Ac arranged nearly one behind the other, in a very weakly curved line; male genital plate anterior margin straight or slightly concave, female genital plates in anterior part not, or only very weakly narrowed and Ac nearly equal in size). Atractides panniculatus (K. Viets, 1925) and A. rivalis Lundblad, 1956 , two species living in Central-South European springs resp. spring brooks, are similar in integument structure and shape of I-L and palps, often also in a protruding anteromedial margin of the male genital plate. Both species differ from A. cydonius in distinctly major Ac (maximum diameter >> 50) in triangular arrangement (posterior margin of Ac-1 separated from anterior margin of Ac-3 by narrow interspace).

Habitat: Crenobiont, springs at middle elevations, 400-1000 m.

Distribution: Calabria, Pollino mountains and neighbouring Pellegrino area.

Fig. 9: Atractides cydonius sp. nov., type series (I 1106). A, ♀ palp medial; B, ♀ genital and postgenital field; C, ♂ genital and postgenital field; D, ♀ I-L-5/6. Scale bars: 100 µm.