Hydrodroma rheophila Cook, 1967

Gerecke, Reinhard, 2017, The water mites of the genus Hydrodroma (Acari, Hydrachnidia, Hydrodromidae) in Europe and Africa, Ecologica Montenegrina 13, pp. 1-24 : 19

Hydrodroma rheophila Cook, 1967

( Figs 7 C-H)

Type series ( not examined): India, Maharashtra state, coll. Cook, FMC. Holotype ♀, small stream five miles west of Wai, gravel bar, 13.03.1963, Collection 90; paratypes: same site as holotype, 2 ♂♂; 2 ♀♀; headwaters of Krishna river near Wai , Collection 22, 29.11.1962, 3 ♂♂; 2 ♀♀, 15.12 1962, 1 ♀; Ghod river 42 miles northeast of Poona , Collection 30, 1 ♀; 14 miles north of Ahmadnager , small spring, Collection 67, 04.02.1962 1 ♂; 1 ♀; 15 miles south of Poona , small stream, gravel bar, 05.03.1963, Collection 87, 1 ♂; 2 ♀♀.

Material examined: Greece, Lesbos , stream Mylopotamos. 06.05.2000 coll. Smit, 3 ♀♀ .

Discussion: As observed by Cook (1967), this species is very similar to the African H. perreptans in the widely reduced swimming setation ( Figs 8 F-H). The females from Lesbos resemble H. perreptans also in the rather large leg claws (L about 50 µm, L ratio claw/segment 5, 20-27 %), and in the heterogeneous integument structure, with larger papillae surrounded by six small, little prominent elevations. However, in the investigated specimens, the large papillae ( Figs 7 C-D) are more flattened and rounded and less densely arranged than in H. perreptans . The key difference to H. perreptans is found in the stouter palp, in particular segment P-4 – L/H measurements of a lesbian specimen are: P-1, 0.8; P-2, 1,4; P-3, 0.9; P-4, 3.7; P-5, 3,7 (compare Fig. 7 E with Fig. 2 F ).

Biology and distribution: As in the African H. perreptans , leg morphology and setation is an obvious adaptation to life in running waters. After the original description from India recorded also from Iran, Oman, Taiwan (with a question mark) and the island of Lesbos in the Aegean Sea (the outpost population discussed here).

Figures

Figure 2. A-D: Hydrodroma despiciens, neotypes, Denmark. A. male, integument papillae near lateral eye in tangential view; B. male, integument in top view; C. male, anterior coxal plate with medial setal tubercles on Cx-I; D. female, genital field; E. female, integument in tangential view; F. male, chelicera.

Figure 7. A-B. Hydrodroma liberiensis, integument papillae in tangential and top view. A. holotype male; B. paratype female. C.-H. H. rheophila, female from Lesbos (photographs and drawings: Vladimir Pešić). C. integument in tangential view; D. integument in top view (magnification as in C.); E. palp; F. II-L-4-5; G. III-L-4-6; H. IV-L-4-6.

Figure 8. Hydrodroma reinhardi, paratype male. A. Cx-I+II; B. genital field; C. folded integument area; D. integument in top view.