Arrenurus tenuicollis lacustris, Smit, 2020

Smit, Harry, 2020, New records of the water mite genus Arrenurus Dugès, 1834 from South America (Acari: Hydrachnidia: Arrenuridae), with the description of five new species and one new subspecies, Acarologia 60 (2), pp. 371-389 : 386-387

Arrenurus tenuicollis lacustris n. subsp.

Zoobank: A4AF299B-4D24-47FD-BA00-03E5EA8137CD

( Figure 11 )

Material examined — Holotype male, Lago Hess, Nahuel Huapi NP, Río Negro Province, Argentina, 41°22’1,16” S, 71°44’12,35” W, 17-xi-1999 ( MBR) . Paratypes: three females ( MBR), 2 females ( RMNH), same data as holotype ; six males, 41 females, Small lake about 15 km N of Villa La Angostura, along Ruta 234, Lanín NP, Neuquén Province, Argentina, 15-xi-1999 ( RMNH).

Diagnosis — Dgl-1 not visible in dorsal view.

Description — Male: Idiosoma yellowish, dorsally 988 (911-1045) long and 494 (462-478) wide, ventrally 974 (919-956) long. Dorsal shield incomplete, 332 (308-336) wide; distance dorsal shield – anterior idiosoma margin 186 (170-203). Idiosoma without humps, Dgl-1 not visible in dorsal view. Gnathosomal bay narrow V-shaped. Cauda relatively long with straight lateral margins. Posterior margin with a shallow indentation, in posterior part of cauda no glandularia visible in dorsal view. Posterior margin lateral of the posterior shallow indentation with very fine setae. Gonopore 44 long, genital field rather broad, 283 wide, swollen and therefore visible in dorsal view. Length of P1-5: 28, 62, 42, 68, 41. P2 with a small patch of setae, anterior setae relatively long; near dorsal margin three long setae. Length of I-leg-4-6: 122, 130, 138. Length of IV-leg-4-6 144, 142, 140; IV-leg-4 without a spur. Legs with numerous swimming setae.

Female: Idiosoma 802 (745-899) long and 644 (608-680) wide, ventrally 826 (729-879) long. Idiosoma slightly truncated posteriorly. Dorsal shield complete, 599 (551-672) long and 502 (502-547) wide. Gnathosomal bay narrow V-shaped. Medial margin of fourth coxae longer than medial margin of third coxae. Medial distance of fourth coxae about the same size of width of one gonopore valve. Length of P1-5: 28, 66, 50, 72, 44; palp as in male. Length of I-leg-4-6: 120, 120, 150. Length of IV-leg-4-6: 144, 142, 140.

Etymology — Named for its occurrence in lakes.

Remarks — A difference with all known subspecies of Arrenurus tenuicollis is that Dgl-1 are not visible in dorsal view in the new subspecies. The male of A. tenuicollis tenuicollis K. Viets, 1936 has a small hump near the anterior idiosoma margin, a narrower, posteriorly more widened cauda compared to the new subspecies, A. tenuicollis megacercus K. Viets, 1954 and A. tenuicollis orthocercus both have the cauda with a posterolateral extension (absent in the new subspecies), additionally A. tenuicollis othocercus has IV-leg-4 with a spur, A. tenuicollis megaluroides Lundblad, 1944 has the idiosoma with lateral extensions (absent in the new subspecies) and near the anterior idiosoma margin there is a small to large, rounded to pointed hump (no hump in the new subspecies), A. tenuicollis gibberipalpis Lundblad, 1944 has a pointed hump near the anterior idiosoma margin (absent in the new subspecies), P2 with a large patch of setae (smaller in the new subspecies) and the accompanying setae of Dgl-3 are distanced from the glandularia (much closer to the glandularia in the new subspecies), A. tenuicollis acornutus has the anterior part of the idiosoma distinctly set off from the idiosoma (not set off in the new subspecies) and smaller genital plates, A. tenuicollis haitiensis Lundblad, 1944 has the idiosoma with small anterior humps, a more pointed dorsal shield, the postocularia are more distanced from Dgl-2 and P2 has a larger patch of setae. The female has been described for a number of subspecies, the known females have larger genital plates compared to the new subspecies. Only the A. tenuicollis gibberipalpis female has similar genital plates, but in this subspecies P2 has a much larger patch of setae.

Figures

Figure 11 Arrenurus tenuicollis lacustris n. subsp. A-D holotype male, E paratype female. A – dorsum; B – venter; C – detail of cauda; D – palp; E – venter. Scale bars: A-B, E = 200 µm, C = 100 µm; D = 50 µm.