Atractides (s. str.) fluviatilis ( Szalay, 1929 )

Gerecke, Reinhard, 2021, The water mites of the family Hygrobatidae (Acari, Hydrachnidia) in Italy, Zootaxa 5009 (1), pp. 1-85 : 22-23

Atractides (s. str.) fluviatilis ( Szalay, 1929)

(Figs 11; 30 R-S)

Material examined: Sardegna: I TG 16-02, 3/12/1; Sicilia: Etna, Iblei, Peloritani, Madonie, Western Mountains. I 109, 2/0/0 slide; I 134, 3/0/0 slide; I 178, 2/6/0 slide; I 184, 1/1/0 slide; I 580, 1/0/0 slide. 6 sites, 32 specimens .

Remarks: As the variability of this species is still little documented, a description and measurement ranges are given for the specimens 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. Venter: Figs 11 C, F. Coxae in three groups, without secondary sclerotization. Posteromedial margin Cx-I+II straight or slightly indented. Genital field with small, round acetabula (maximum diameter 20-40) arranged in a weakly curved line (Figs 11 C-E). I-L-5-6: Fig. 11 B. 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 (Fig. 11 A) without 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 slightly shorter than the preceding ones).

Males (n = 6, I-L: 9): Idiosoma L/W 450-640/380-480, coxal field L/W 290-345/300-405; Cx-I+II mL 80-125, lL 185-220, W 275-320. I-L-5 dL/vL 158-196/103-128, ratio 1.5-1.6, distal sector 20-32 %; HA 30-48, HB 46-63, HC 50-78, ratio dL/HB 3.1-3.6; S-1 L/W 78-113/8-10, ratio 8.9-12.3; S-2 L/W 73-85/10-14, ratio 6.0-7.3; distance S-1-2, 18-28, L ratio S-1/-2, 1.2-1.3; I-L-6 dL 118-158, HA 24-30, HB 16-23, HC 18-24; ratio dL/HB 7.0-8.5; dL ratio I-L-5/6, 1.21-1.34. Genital field L/W 80-105/88-115, anterior margin slightly convex, posterior margin with a medial indentation, lateral margins on the level Ac-2-3 nearly straight, converging posteriorwards; gonopore L 45-65, surrounded by about 15 pairs of setae; maximum diameter Ac-1, 25-34; Ac-2, 25-29; Ac-3, 23-38. Chelicera L 200, L/H 5.6, basal segment/claw 2.3. Palp total L 266-330; L/H (ratio, rel. L [%]) P-1, 28-38/25-31 (1.0-1.2, 10- 11); P-2, 60-75/45-59 (1.3-1.4, 22-23); P-3, 60-78/40-50 (1.5-1.6, 23-24); P-4, 88-105/34-41 (2.6-2.7, 32-33); P-5, 28-35/11-13 (2.2-3.0, 10-12); L ratio P-2/P-3, 0.93-1.02; P-2/P-4, 0.66-0.71; P-3/P-4, 0.66-0.71. P-2 ventral margin slightly convex in distal half; P-3 ventral margin nearly straight; P-4 dorsally with dense cover of fine, hair-like setae.

Females collected with fluviatilis males (n = 7): Idiosoma L/W 520-750/380-550, coxal field L/W 320-430/350- 500; Cx-I+II mL 90-130, lL 190-260, W 290-380. I-L-5 dL/vL 195-220/130-168, ratio 1.3-1.6; HA 48-60, HB 55-66, HC 70-80, ratio dL/HB 3.3-3.6; S-1 L/W 93-113/8-11, ratio 8.7-13.4; S-2 L/W 80-93/11-14, ratio 6.0-7.1; distance S-1-2, 20-31, L ratio S-1/-2, 1.1-1.3; I-L-6 dL 133-173, HA 24-29, HB 15-20, HC 19-25; ratio dL/HB 6.6-10.2; dL ratio I-L-5/6, 1.23-1.64. Genital field L/W 120-175/100-110, pregenital sclerite narrow, little curved, postgenital sclerite compact, irregular, genital plates L/W 100-110/30-40, anteriorly and posteriorly rounded, each bearing about 10 fine, hair-like setae; Ac similar in size; maximum diameter Ac-1, 30-38; Ac-2, 28-36; Ac-3, 25-40. Palp total L 306-360; L/H (ratio, rel. L [%]) P-1, 31-36/29-33 (1.0-1.2, 10); P-2, 65-85/46-60 (1.3-1.5, 21-24); P-3, 75-90/35-44 (1.9-2.2, 24-26); P-4, 95-111/26-33 (3.4-3.8, 31-32); P-5, 35-38/10-13 (2.8-3.7, 10-12); L ratio P-2/P- 3, 0.82-0.94; P-2/P-4, 0.65-0.76; P-3/P-4, 0.78-0.83.

In their measurements, male specimens from I 109 and I 134 tend to grade towards A. pollux , while females from the same sites are clearly distant from that species in by far major dimensions of appendages, presence of a hump near S-1 insertion on I-L-5, and a major distance S-1-2 (> 40).

Habitat: Rhithrobiont. In middle order streams at middle altitudes, in the Sicani mountains (I 580) in a rheocrene.

Distribution: Ascertained from the stream Garam in Hungary (Komitat Bars) ( Szalay 1929, 1935); all other records, including the ones from Croatia and Israel cited by Gerecke (2003) refer to other species or are questionable. First records from Italy.