Hydrodroma longiseta K. Viets, 1954

Pešić, Vladimir & Smit, Harry, 2022, Water mites of the genusHydrodroma Koch, 1837 (Acari, Hydrachnidia: Hydrodromidae) from Argentina, with description of two new species, Acarologia 1837 (1), pp. 68-83 : 72

Hydrodroma longiseta K. Viets, 1954 stat. nov.

Figure 3

Material examined — Argentina, Prov. Entre Rios, ditch Brazo Largo, Delta de Paraná, N of Zarate, 33°54.621 S, 58°51.154 W, 6 Nov. 1999, leg. Smit, 1♂, dissected and slide mounted ( RMNH).

Morphology — Male — Integument papillae apically rounded ( Figure 3B). Posteromedial projections of Cx-I short, separated by a fine membranous line ( Figure 3A). Genital flaps each with 62 Ac in at most 5 longitudinal rows, and 25 setae, all hollow ( Figure 3A). Legs with relatively small claws (L 17-22 µm, ratio claw L/segment 5 L 10-13 %). Leg setae numbers: II-L-posterior 0; III-L-4 posterior 5-6; III-L-5 posterior 5; IV-L-4 anterior 5-6, posterior 5; IV-

L-5 anterior 0, posterior 4. P-2 with three pectinate distal setae on medial surface, dorsodistal seta hair-like, long and slender ( Figure 3B).

Measurements: Idiosoma L 806, W 650. Coxal field L 353; Cx-III W 347; L Cx-I+II, 183, Cx-III+IV, 191. Coxal setae numbers: Cx-I, 14-15; Cx-II, 17; Cx-III, 15-16; Cx-IV, 12. Genital plate L 156-162. Ejaculatory complex L 130.

Gnathosoma vL 152; chelicera total L 193, L basal segment 153, claw 41, L ratio basal segment/claw 3.8. Palp total L 325, dL/H, dL/H ratio: P-1, 34/31, 1.13; P-2, 58/45, 1.27; P-3,

28/39, 0.72; P-4, 138/30, 4.6; P-5, 67/26, 2.6; L ratio P-2/P-4, 0.42. dL I-L-2-6: 64, 83, 128,

158, 159; claw L 20, – 12.8 % L I-L-5. dL II-L-2-6: 75, 94, 159, 190, 191; claw L 20, – 10.7

% L I-L-5. dL III-L-1-6: 47, 72, 91, 150, 169, 163; claw L 17, – 10.2 % L I-L-5. dL IV-L-2-6:

100, 128, 197, 217, 200; claw L 22, – 10.1 % L I-L-5.

Remarks — Our specimen is provisionally assigned to Hydrodroma longiseta K. Viets,

1954. This taxon was originally described by K. Viets (1954a) as a subspecies of H. despiciens . Hydrodroma longiseta resembles H. despiciens in shape of the coxal field, with short and medially directed posteromedial projections of Cx-I, but differs in the absence of swimming setae on II-L and in the shape of the palp with a long and slender, hair-like dorsodistal pectinate seta on the medial surface of P-2 (see Figures 14a-c in K. Viets 1954a). In regard to these differences, there is no reason to support the assignment of this taxon as subspecies of H. despiciens . In the shape of the coxal field and the palp our specimen from Delta de Paraná matches the original description. Anyhow, the variability of more specimens including material from the locus typicus needs to be examined to clarify the taxonomy of this species.

Distribution — Brazil („ H. despiciens longiseta “ in K. Viets 1954a), Argentina (this study).