Hydrodroma ventana Pešić & Smit, 2022

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 : 78-82

Hydrodroma ventana Pešić & Smit sp. nov.

Zoobank: 2018E6DD-D27A-4202-A2AF-103611065A51

Figures 7-9

Material examined — Holotype ♂ ( NBR), Argentina, Prov. Buenos Aires, Arroyo Sauce Grande, Sierra de la Ventana , 10 Nov. 1999, leg. Smit, dissected and slide mounted . Paratypes: 2♂, 2♀, same place and data as holotype, 1 ♂, 1♀ dissected and slide mounted ( RMNH); 1♀, Arroya Naposté, Sierra de la Ventana, Estancia Funke E of Torquist, 38°07.998 S, 62°05.229

W, alt. 334 m, 8 Mar. 2018, leg. Smit ( NBR).

Diagnosis — Main integument papillae flattened, surrounded by six small, little prominent elevations ( Figures 9 B-C), in tangential view short and apically rounded ( Figure 9A). Posteromedial projections of Cx-I short. Genital plates with 37–45 pairs of Ac in at most 4 longitudinal rows. Legs with relatively long claws (L 39-42; L ratio claw/segment 5, 13-22 %). Leg setae

– integument papillae, in tangential view; B-C – integument papillae, in top view; D – gnathosoma; E – ejaculatory complex, anterior view; F

– ejaculatory complex, posterior view.

numbers: II-L-posterior 0; III-L-4 posterior 2-4; III-L-5 posterior 2-3; IV-L-4 anterior 1-3, posterior 3-4; IV-L-5 anterior 0, posterior 1-3.

Description — Posteromedial projections of Cx-I short, medially separated by a fine membranous line. Genital flaps with rounded lateral and strongly concave medial margins, each with 37-45 Ac and 23-28 hollow setae. P-2 with three pectinate mediodistal setae similar in size.

Male (holotype ; in parentheses some measurements of paratype, n = 1): Idiosoma L 1112 (875), W 931 (838). Coxal field L 447; Cx-III W 470; L Cx-I+II 230, Cx-III+IV, 219. Coxal setae numbers: Cx-I, 17 (15); Cx-II, 23 (23); Cx-III, 14 (12); Cx-IV, 14-15 (17). Genital plate

L 188 (173). Ejaculatory complex (184).

Gnathosoma vL 167; chelicera total L 239, L basal segment 188, claw 52, L ratio basal segment/claw 3.6. Palp total L 328, dL/H, dL/H ratio: P-1, 42/33, 1.27; P-2, 50/47, 1.07 (61/48, 1.26); P-3, 33/42, 0.78 (31/47, 0.67); P-4, 142/33, 4.3 (147/34, 4.3); P-5, 61/17, 3.5 (61/16,

3.9); L ratio P-2/P-4, (0.41). dL I-L-2-6: 66, 88, 144, 177, 191; claw L 39, – 22.0 % L I-L-5.

dL II-L-2-6: 91, 119, 188, 223, 223; claw L 39, – 17.5 % L I-L-5. dL III-L-2-6: 94, 125, 188,

215, 209; claw L 40.6, – 18.9 % L I-L-5. dL IV-L-2-6: 125, 172, 253, 266, 231; claw L 42.2, –

15.9 % L I-L-5.

Female: Idiosoma L 1395, W 1156. Coxal field L 528; Cx-III W 506; L Cx-I+II 263, Cx-III+IV, 264. Coxal setae numbers: Cx-I, 14-18; Cx-II, 24; Cx-III, 12 Cx-IV, 16. Genital plate large, L 192.

Gnathosoma vL 213; chelicera total L 275, L basal segment 217, claw 59, L ratio basal segment/claw 3.7. Palp total L 371, dL/H, dL/H ratio: P-1, 42/42, 1.0; P-2, 70/52, 1.36; P-3,

38/48, 0.77; P-4, 155/34, 4.5; P-5, 66/17, 3.8; L ratio P-2/P-4, 0.45. dL I-L-2-6: 77, 105, 170,

216, 200; claw L 41, – 18.8 % L I-L-5. dL II-L-2-6: 100, 131, 226, 263, 228; claw L 42, – 16.0

% L I-L-5. dL III-L-2-6: 116, 141, 212, 250. 228; claw L 42.2, – 16.9 % L I-L-5. dL IV-L-2-6:

147, 200, 293, 313, 265; claw L 41, – 13.0 % L I-L-5.

Etymology — Named after the Sierra de la Ventana, the name is a noun in apposition.

Discussion — The new species resembles H. argentinensis sp. nov. in the absence of swimming setae on II-L and a similar shape of the palp (L/H ratio P-4 ˂ 6.0; three pectinate distal setae on P-2 similar in size). The new species differs from H. argentinensis sp. nov. in a lower number of genital acetabula (˂ 50 Ac), reduced number of swimming setae on III/IV-L (less than 4 on both posterior III-L-4 and anterior IV-L-4), legs with a relatively large-sized claw (L ratio claw/segment 5, 13-22 %) and in the shape of integument papillae (more flattened, in tangential view short, and less densely arranged than H in. argentinensis sp. nov., compare figures 4C-D with 9A). Moreover, the new species differs in the absence of swimming setae on the anterior IV-L-5 (see under H. argentinensis sp. nov. about variation in the swimming setation of the latter species).

In comparison with the six known South American subspecies of H. despiciens , the new species is most similar to H. despiciens macronyx K. Viets, 1954a , described from northeast Brazil (Pernambuco). The latter subspecies is distinguished from the new species from Argentina in more slender palp segments, especially P-4 (L 208 µm; L/H ratio P-4 6.3) and shortened swimming setae on III/IV-L.

Distribution — Argentina.