Atractides (s. str.) inflatipalpis K. Viets, 1950

Gerecke, Reinhard, 2021, The water mites of the family Hygrobatidae (Acari, Hydrachnidia) in Italy, Zootaxa 5009 (1), pp. 1-85 : 26-29

Atractides (s. str.) inflatipalpis K. Viets, 1950

(Figs 13-14; 29 R; 32 I-L)

Material examined: Calabria: I 101, 1/0/0 slide; I 419, 2/3/0 slide; I 428, 1/6/0 slide; I 447, 1/3/0 slide; Lazio: I 1289, 1/1/0 slide; I 1291, 1/1/0 slide; Sicilia: All parts except for Iblei. I 46, 2/5/0 slide; I 78, 2/4/5, slide; I 83, 1/1/0, slide; I 109, 1/0/0 slide; I 131, 7/20/1 slide; I 132, 5/7/0 slide; I 133, 11/16/0 (5/6/0 slide); I 134, 2/0/0 slide; I 137, 10/12/1, slide; I 165, 3/18/0 slide; I 237, 15/11/6 slide; I 299, 1/0/0 slide; I 502, 1/1/0 slide; I 503, 2/1/0 slide; I 656, 0/3/0 slide; I dp 10, 1/1/0 slide; I dp 66, 1/7/1 slide; I dp 67, 5/0/0 (4/0/0 slide); I dp 76, 2/7/0 slide; I dp 85, 1/15/0; I dp 94, 4/6/0 slide; I dp 98, 1/0/0 slide. 28 sites, 248 specimens.

Previously published records from Italy: Abruzzo (K. Viets 1955); Sardegna ( Gerecke 2014b)

Remark: As the variability of this species is little documented, measurement ranges (restricted to specimens from site I 131) and morphological details are here given for populations from the study area.

Both sexes: Integument lineated, muscle insertions and excretory pore unsclerotized, Vgl-1/2 separate. Glandularia small, round, also dorsocentral ones with relatively short setae. Coxae in three groups, without secondary sclerotization. Posteromedial margin Cx-I+II straight or slightly indented. Genital field with small, rounded acetabula (maximum diameter 20-40) arranged in a weakly curved line. I-L-5 ventral and dorsal margins diverging from base to S-1 insertion, but here not forming a prominent hump; S-1 distally equally narrowed, apically oblique truncated, forming a fine denticle on the adaxial side; S-2 distinctly shorter, tip bluntly pointed. I-L-6 curved, maximum H in basal part, distally equally narrowed. Palp with sexual dimorphism; P-4 maximum H near proximoventral seta, sword seta halfway between ventral seta insertions - these dividing ventral margin into subequal sectors (in general, the distal sector slightly shorter than the preceding ones).

Males (n = 8, selected palp and I-L characters 20): Idiosoma L/W 450-580/300-420, coxal field L/W 250- 315/380-360; Cx-I+II mL 80-100, lL 155-190, W 250-285. I-L-5-6: Figs 13 C-D. I-L-5 dL/vL 140-184/96-122, ratio 1.4-1.5; HA 40-46, HB 46-55, HC 55-70, ratio dL/HB 2.9-3.5; S-1 L/W 78-98/6-8, ratio 11,3-12.4; S-2 L/W 65-81/10 (N.B.: in Gerecke 2014b erroneous, 75-85/44-15 – correct: 75-85/14-15), ratio 6.5-7.5; distance S-1-2, 15-25, L ratio S-1/-2, 1.1-1.2; I-L-6 dL 108-144, HA 25, HB 18-19, HC 19-20; ratio dL/HB 6.1-7.3; dL ratio I-L- 5/6, 1.28-1.35. Genital field (Fig. 13 A-B) L/W 74-87/74-90, rounded, anterior margin slightly convex or nearly straight, posterior margin with a shallow medial indentation; gonopore L 45-50, surrounded by about 20 pairs of setae; maximum diameter Ac-1, 22-25; Ac-2, 20-28; Ac-3, 22-33. Palp (Figs 13 E-F) total L 233-290; L/H (ratio, rel. L [%]) P-1, 25-35/24-26 (1.1-1.4, 11-13); P-2, 55-63/44-50 (1.2-1.4, 22-24); P-3, 48-73/35-40 (1.3-1.8, 20-23); P-4, 78-98/30-35 (2.4-3.3, 33-34); P-5, 28-30/10-11 (2.7-3.0, 10-12); L ratio P-2/P-3, 0.86-1.16; P-2/P-4, 0.64-0.71; P-3/P-4, 0.60-0.76. P-2 ventral margin proximally concave, distally forming a rounded projection; P-4 with dense cover of fine, hair-like setae.

Fig. 13: Atractides inflatipalpis ♂ (I 131). A, venter (genital setae omitted); B, genital field; C, I-L-5/6; D, I-L-6 separate; E, palp medial (specimen with weakly developed P-2-projection); F, palp medial (specimen with strongly developed P-2 projection, I 1291). Scale bars: 100 µm.

Fig. 14: Atractides inflatipalpis ♀ (I 1291). A, I-L-5/6; B, palp medial; C, genital field. Scale bar: 100 µm

Females (n = 7, selected palp and I-L characters 17): Idiosoma L/W 720-830/520-600, coxal field L/W 350- 380/430-470; Cx-I+II mL 85-110, lL 205-220, W 320-360. I-L-5-6: Fig. 14 A. I-L-5 dL/vL 208-220/130-146, ratio 1.4-1.6; HA 51-58, HB 58-63, HC 78-83, ratio dL/HB 3.4-3.8; S-1 L/W 105-113/9-11, ratio 10.0-12.9; S-2 L/W 86-94/14-15, ratio 5.8-6.8; distance S-1-2, 24-31, L ratio S-1/-2, 1.2-1.3; I-L-6 dL 163-175, HA 23-28, HB 16-18, HC 18-20; ratio dL/HB 9.3-10.6; dL ratio I-L-5/6, 1.21-1.31. Genital field L/W 150-160/90-104, genital plates (Fig. 14 C) L/W 90-104/28-32, weakly curved, anteriorly and posteriorly rounded, bearing 10-12 pairs of fine, hair-like setae; Ac similar in size, maximum diameter Ac-1, 29-35; Ac-2, 23-30; Ac-3, 30-38. Palp (Fig. 14 B) total L 313- 335; L/H (ratio, rel. L [%]) P-1, 30-35/28-31 (1.0-1.2, 10); P-2, 68-74/46-51 (1.4-1.5, 21-22); P-3, 83-88/38-40 (2.1-2.3, 25-26); P-4, 98-108/28-29 (3.6-3.8, 31-32); P-5, 31-35/11 (2.8-3.1, 10); L ratio P-2/P-3, 0.82-0.85; P-2/P- 4, 0.67-0.72; P-3/P-4, 0.79-0.85. P-2 ventral margin straight or weakly convex; P-3 and -4 slenderer, P-4 dorsal setation less dense than in males.

In a study based on populations collected in Corsica and Sardinia, Gerecke (2014b), found differences in both sexes between A. inflatipalpis and A. valencianus in proportions of I-L-5/6, as well as in the arrangement and shape of setae of these segments, namely of S-1/-2, and also in the shape of the male P-4. However, A. valencianus - / inflatipalpis -like fluviatilis -group populations (with a ventral projection on P- 2 in males) collected in continental Italy and Sicily show intermediate character states in the shape of the male palp as well as in proportions of I-L and its sword setae. For the time being, all male specimens showing the combination of a P-2 with distoventral projection, and presence of 7-8 genital setae between Ac-1 and gonopore in a single row, are here listed under A. inflatipalpis . Males of A. valencianus , the other fluviatilis -like species in Italy (with P-2 distally projecting) bear 12-20 paired genital setae arranged in double or triple lines and posteriorly extending until the anterior margin of Ac-3. Females cannot be identified at species level

A comparison of variability ranges between populations attributed to A. inflatipalpis from Corsica / Sardinia on the one hand ( Gerecke 2014b), and a population from Sicily (I 133, 5 ♂♂, 6 ♀♀), on the other, shows that Corsardinian specimens differ in a wider distance S-1-2 (♂♂, 25-33; ♀♀, 40-58) and males in a relatively longer I-L-6 (L ratio L-L-5/6 <1.28). Furthermore, dimensions of palp segments are major in both sexes (with a slight overlap in males: palp total L ♂♂ 285-338, ♀♀ 348-432). If Sicilian populations from sites other than I 131 are screened, these differences find widely confirmation, but measurements of single specimens fall within the Corsardinian variability range. These data suggest that the fluviatilis group represents a clade embracing more species than recognized at present, based on adult morphology alone .

Habitat: Rhithrobiont. In middle order streams at middle and low altitudes (mean 390 m), in the Peloritani and Madonie mountains, small populations found in rheocrenes at three occasions.

Distribution: Mediterranean ( Greece, Bulgaria, Italy, France).