Hydrodroma zhokhovi Tuzovskij, 2014

Gerecke, Reinhard, 2020, The early derivative water mites (Acari: Hydrachnidia, superfamilies Eylaoidea, Hydrachnoidea and Hydryphantoidea) of Madagascar, Zootaxa 4727 (1), pp. 1-77 : 24-26

Hydrodroma zhokhovi Tuzovskij, 2014

Figs 12 k – n , 13 a – c

Hydrodroma despiciens Koenike, 1898 (?)

Hydrodroma despiciens Gerecke 2004 partim

Material examined: MD 077, 13.09.2001 F. Dauphin (Tulear), Mandena (QMM area), ditch at right border of R Amendano, 10 m, (0/2/0) in liquid, Ac 1431; MD 081a , 14.09.2001 F. Dauphin (Tulear), Mandena (QMM area), lake situated inland from coastal lake at mouth of R Amendano (MD 080), 2 m, riparian vegetation, (1/2/3) slidemounted, Ac 1300 – 1303; (1/9/0) in liquid, Ac 1432; MD 081b, same site and date, open water, (2/8/0) in liquid, Ac 1433; MD 104 , 06.10.2001 Ankaratra (Antananarivo), Reserve Manjakatompo, Lac Froid , 1640 m, (7/3/1) slide mounted, Ac 1304 – 1313; (15/40/0) in liquid, Ac 1434; MD 105 , 06.10.2001 Ankaratra (Antananarivo), rheohelocrene at SW border of MD 104, (0/1/0) in liquid, Ac 1435; MD 226, Ionilahy (Fianarantsoa), lake Ranovory below village, 211 m, 21°43’49.8’’ S 047°36’58.6’’ E, 22.04.2011 (1/1/1) in liquid, Ac 1436; MD 235, Moramanga, Plaine de Marovoay , X 1949 Paulian leg., (3/1/0) slide mounted, Ac 1314 – 1317; A 01 D Antsiranana, Ankarana (marais) , IX 1946 leg. Millot, (0/1/0) slide mounted, Ac 1296; E 14 E Nossi-Bé, L. Djabol-Bé , IX 1947 leg. Millot, (0/3/0) slide mounted, Ac 1297 – 1299; SMF 51126, 51140–51141, “Tilapia Teich bei Forststation Mandena bei Fort- Dauphin i. SO-Madagaskar, Starmühlner leg., 9.8.1958 (MD 203) 1978 – 1980 ”, “ Hydrodroma capensis ”, (1/2/0); SMNH 43329, “Majunga”, “ Hydrodroma capensis ”, (0/1/0) .

Description: Colour pale red. Integumental papillae short, slightly curved ( Fig. 12 l – n ). Lateral eye lens diameter anterior 40 – 70, posterior 30 – 60, separation 50 – 150. Medial margin of Cx-I with distinct projections associated with setal bases; tips Cx-I with very few (2 – 4) strong setae, a few further strong setae posterolaterally on Cx-I, and antero- and posterolaterally on Cx-II and –III ( Figs 12 k , 13 a ). Medial margin of Cx-I with 5 – 9, posterior margin of Cx-IV with 10 – 21 setae in a single, slightly irregular row. Posterolateral apodeme of Cx-IV long, oblique to the median axis ( Fig. 13 a ). Swimming setae (anterior/posterior) II-L-5, 0/1 – 2; III-L-4, 0/5 – 15; III-L-5, 0/5 – 12; IV-L-4, 7 – 14/7 – 14; IV-L-5, 0/5 – 10. Leg claw length (all legs) 23 – 35; L ratio claw/ I-IV-L-5, 6 – 13 %. Leg segments slender (e.g., L/H ratio I-L-5, 4.8 – 6.5; II-L-5, 6.4 – 7.7; III-L-5, 5.6 – 7.3; IV-L-5, 7.0 – 8.4–see Fig. 13 b – c ).

Measurements: Male: Idiosoma L/W 800 – 1500/750 – 1250; Cx-I+II, 240 – 310/150 – 190; Cx-III+IV, 250 – 300/270 – 310; genital plate 230 – 275/90 – 125, genital field with 64 pairs of acetabula (5 – 9 per transect) and 60 – 90 pairs of medial setae. Distal leg segments, given as L/H (ratio): I-L-4, 160 – 215/50 – 60 (3.2 – 3.6); I-L-5, 205 – 305/40 – 50 (5.1 – 6.5); II-L-4, 255 – 305/53 – 65 (4.5 – 5.1); II-L-5, 280 – 360/43 – 50 (6.6 – 7.6); III-L-4, 215 – 285/47 – 60 (4.3 – 5.4); III-L-5, 260 – 330/40 – 50 (6.0 – 7.3); IV-L-4, 285 – 365/48 – 60 (5.5 – 6.2); IV-L-5, 305 – 375/43 – 50 (7.2 – 8.3). Mouthparts: Gnathosoma L 195 – 240; chelicera L 288 – 340, L/H 4.3 – 5.4, basal segment/claw L ratio 3.7 – 4.3; palp total L 394 – 508; L/H (ratio) P-1, 43 – 58/59 – 70 (0.7 – 0.9); P-2, 68 – 85/53 – 70 (1.1 – 1.3); P-3, 45 – 55/53 – 65 (0.8 – 1.0); P-4, 165 – 228/40 – 50 (4.1 – 4.9); P-5, 70 – 90/18 – 23 (3.3 – 4.5); L ratio P-2/P-4, 0.3 – 0.4, P-4/P-5, 2.4 – 2.7.

Female: Idiosoma L/W 750 – 1400/650 – 1250; Cx-I+II, 240 – 310/160 – 210; Cx-III+IV, 250 – 320/260 – 350; genital plate 190 – 260/80 – 140, genital field with 70 – 135 pairs of acetabula (6 – 9 per transect) and 38 – 54 pairs of medial setae. Distal leg segments, given as L/H (ratio): I-L-4, 150 – 225/48 – 68 (3.0 – 3.6); I-L-5, 190 – 275/40 – 50 (4.8 – 6.1); II-L-4, 218 – 330/50 – 70 (4.3 – 4.9); II-L-5, 255 – 380/40 – 53 (6.4 – 7.7); III-L-4, 200 – 315/45 – 70 (3.9 – 5.7); III-L-5, 245 – 355/35 – 55 (5.6 – 7.); IV-L-4, 245 – 385/45 – 75 (5.1 – 6.8); IV-L-5, 265 – 420/38 – 50 (7.0 – 8.4). Mouthparts: Gnathosoma L 180 – 260; chelicera L 280 – 360, L/H 4.1 – 5.1, basal segment/claw L ratio 3.5 – 4.2; palp total L 378 – 533; L/H (ratio) P-1, 44 – 60/58 – 70 (0.7 – 0.9); P-2, 68 – 90/50 – 75 (1.2 – 1.4); P-3, 40 – 60/48 – 78 (0.7 – 1.0); P-4, 160 – 233/39 – 58 (4.0 – 4.8); P-5, 48 – 95/18 – 23 (2.5 – 4.5); L ratio P-2/P-4, 0.3 – 0.4, P-4/P-5, 2.3 – 3.7.

Remarks: The populations summarized here under the name of H. zhokhovi cover a wide range of variability in size and proportions of appendage segments, but agree with the original description concerning the diagnostic features given above. A difference in comparison with the original description ( Tuzovskij 2014), the relatively prominent setal bases at medial margin of Cx-I of the Madagascan specimens, is probably caused by the treatment of the specimens of the type series (Tuzovski, pers. comm.). These projections may disappear, or become difficult to see, in slide mounted specimens due to cover slide pressure. In swimming setation (two inserting posterior on II-L-5, absence from anterior IV-L-5), H. zhokhovi is similar to H. capensis (K. Viets, 1914) , recorded from many parts of continental Africa, but with its presence ascertained for the Cape region only (Gerecke 2017). The latter differs in lower numbers of genital setae (<40) and acetabula (<65), and in more elevated integumental papillae. Revision of slide material from SMNH and the SMF show that records published from Madagascar under the name of H. capensis must be attributed to H. poseidon . This interpretation should be substantiated by revision of further material from the corresponding sites–specimens of H. zhokhovi could be mixed in.

Habitat: Larger standing waters.

Distribution: Madagascar, scattered records from all over the island, from sea level to 1640 m asl.

Figures

FIGURE 12. Family Hydrodromidae, genus Hydrodroma. a.–e. H. lasioderma (MD 154b); a.–b. female and male Cx-I+II; c.–e. integument papillae in various views; f.–i. H. mesembrina (MD 151); f. female Cx-I+II; g.–i. integument papillae in various views; k.–n. H. zhokhovi female; k. Cx-I+II; l.–n. integument papillae in various views.

FIGURE 13. Family Hydrodromidae, genus Hydrodroma. a.–c. H. zhokhovi, female (MNHN A1D); a. coxal and genital field; b. IV-L-4–6; c. III-L-4–6; d.–e. H. amoenoderma, female (MD 097); d. IV-L-4–6, e. III-L-4–6.