Omanohydracarus arabicus, Gerecke, 2004

Gerecke, Reinhard, 2004, Water mites from spring- and ground-water habitats in the Sultanate of Oman, Journal of Natural History 38 (22), pp. 2833-2849 : 2839-2843

Omanohydracarus arabicus sp. nov.

( figures 3–6 )

Type series. HOLOTYPE: „, OMAN 96-51. Wadi Taww , S of Halban, 1.00 m below sediment surface (water loamy); UTM 0604748/2606459 (23‡34'N, 58‡01'E), 28.4‡C, 568 M S cm 21, 28 March 1996; slide mounted in Hoyer’s fluid. PARATYPE: ”, OMAN 96-125. Wadi Mawhal, open well at Mouhadeth; UTM 0582731/2590745 (23‡25'28̎N, 57‡48'35̎E); cv. net; 28.0‡C, M S cm 21, 9 April 1996, slide mounted in Euparal.

Diagnosis. As given for the subfamily.

Description. Male: idiosoma (ventral view: figure 3A ) L/W 810/710, sclerotized areas with a honeycomb-like surface structure (ventrally covering the whole surface including the postgenital area); dorsal shield ( figure 3B ) L/W 805/610, consisting of an oval plate perforated by numerous, irregularly arranged round ‘windows’ with papillate membranous surface; distance between the lateral tips of coxae: Cx-1 325, Cx-2 472, Cx-3 510, Cx-4 570; distance between posterior tips of Cx-4 325; all legs lacking swimming hairs, with simple claws, I-L-3–5 ( figure 4A ) with long ventral spines inserted on sockets near paired denticles; II-L-3 ( figure 4B ) ventrally with a strongly developed central hump and a strong, curved ventrodistal seta; III-L-3 ( figure 5A ) with two strong, blade-like ventral setae, III-L-4 with a strong, distally curved proximal seta, a stout ventral seta on a distinct socket, and ventrodistally a strongly developed, sword-like, pointed spur; IV-L ( figure 5B ) slender and long, with rather fine setae and short hairs; measurements (segments 1–6, L/H): I-L 42/35, 153/64, 148/60, 192/48, 175/35, 292/40; II-L 82/65, 162/58, 150/68, 175/48, 165/35, 227/35; III-L 2/2 (III-L-1 damaged), 118/64, 78/64, 158/45 (without spur, spur L 83), 158/35, 178/36; IV-L 102/82, 178/63, 168/53, 205/54, 245/40, 232/40; genital field with 9 z 10 knobshaped acetabula arranged between the anterior part of the gonopore and the mediocaudal margins of the Cx-4; gonopore L 114, with rounded anterior, and pointed posterior margins, caudally extending into a longish sclerite; genital skeleton ( figure 3C ) with flat anterior and posterior keels, L 180 M m; gnathosoma ( figure 5C ) short and stout, ventral L 125; chelicera basal segment L 96, H 57, claw L 37; shape and setation of palps as shown in figures 4C and 5C ; segments L/H P-1–5: 33/37, 105/75, 62/50, 125/78, 55/23. P-2 with a pointed ventrodistal extension, P-4 enlarged, forming a curved shield that covers the insertion of P-5, with a pointed dorsodistal extension and a peg-like medial seta; P-5 with a strong dorsal claw.

Female: idiosoma (ventral view figure 6A ) L about 740 (damaged); dorsal shield ( figure 6B ) L/W 660/475, as described for the male, but with membranous ‘windows’ in greater numbers and more densely arranged; distance between posterior tips of Cx-4 210; I- and IV-L similar to male, but II- and III-L more simple in shape and setation ( figures 6D, E ): II-L-3 ventrally with a pair of strong setae inserted on a pair of sockets with strong denticles, but lacking both a distinct central hump and a curved ventrodistal seta; III-L-3/4 without curved setae or sword-like spurs; measurements of segments 1–6, L/H: II-L 62/55, 125/62, 112/50, 125/42, 120/30, 136/25; III-L 75/50, 80/40, 75/45, 115/42, 105/37, 107/30; IV-L 84/54, 112/44, 112/40, 135/78, 162/34, 162/34; genital field embedded into the ventral shield, but with wellrecognizable, curved pre- and postgenitalia, L 197, gonopore enlarged in the centre, but closed in its anterior and posterior parts; 5 z 6 minute, knob-shaped acetabula and 2 z 3 fine hairs between the anterior part of the gonopore and the mediocaudal margin of Cx-4; palp shape and setation as shown in figure 6C , P-2 without a pointed ventrodistal projection, P-4 not forming a shield that covers the insertion of P-5, with a pointed mediodistal extension, paired, setae-bearing ventral projections and a peg-like ventrodistal seta; P-5 slender; segment measurements P- 1–5 L/H 26/40, 92/72, 50/42, 82/37, 50/20.

Discussion. The attribution of the two specimens to one single species is preliminary as they were collected at two different sites. However, differences such as a more simple shape and setation of legs, more extended membranous areas on the idiosoma and a lower number of acetabula are often found as sexual dimorphism in hygrobatoid water mites.

Figures

FIG. 3. Omanohydracarus arabicus sp. nov., male (OMAN 96-51). (A) Idiosoma, ventral view; (B) dorsal shield; (C) genital skeleton, lateral view. Scale bars: 100 Mm.

FIG. 4. Omanohydracarus arabicus sp. nov., male (OMAN 96-51). (A) I-L; (B) II-L; (C) right palp, lateral view. Scale bars: 100 Mm.

FIG. 5. Omanohydracarus arabicus sp. nov., male (OMAN 96-51). (A) III-L; (B) IV-L; (C) gnathosoma and left palp, medial view. Scale bars: 100Mm.

FIG. 6. Omanohydracarus arabicus sp. nov., female (OMAN 96-125). (A) Idiosoma, ventral view; (B) dorsal shield; (C) palp, lateral view; (D) II-L; (E) III-L. Scale bars: 100 Mm.