Hydrachna novaehollandica Smit, 2014, n. sp.
Creators: name: Smit, Harry
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Trombidiformes
Hydrachnidae
Hydrachna
Hydrachna novaehollandica

description: Hydrachna novaehollandica n. sp.
(Figs. 8A–E)
Hydrachna bilobata Lundblad, 1947 (nec Halík, 1940) Hydrachna (? Scutohydrachna) sp. Cook, 1986 Hydrachna spec. Smit, 1992 (part.)
Material examined. Holotype male, Jackeroo’s Waterhole, El Questro Station. The Kimberley, Western Australia, Australia, 15-ix-1998 (WAM). Paratypes: 7 males, 3 females, 3 nymphs (one mounted female WAM, others RMNH), same data as holotype. Other material: Queensland. 0/1/0, Reservoir near Eungella Dam, 10 km W of Eungella, 28-vii-1989; 1/0/0, Catfish Waterhole, Lakefield NP, 15º 3’57.50” S 144º 17’8.43” E, 4-ix-2000; 1/0/1, Hann Crossing (flowing), Lakefield NP, 5-ix-2000; 1/0/0, Dowlings Waterhole, Lakefield NP, 3-ix-2000; 1/2/1, Mt Carbine Dam, Mt Carbine, 16º 32.019 S 145º 0 7.525 E, alt. 358 m asl, 14-x-2005; 0/1/0, Small lake south of Biggenden, along road Biggenden-Maryborough, 25º 33.583 S 152 º 0 7.345 E, 1-xi-2005. Northern Territory. 1/ 0/1, Billabong Yellow Waters, Kakadu NP, 21-vii-1994; 1/0/0, Billabong near Douglas Hot Springs, 1-viii-1994; 2/ 0/5, Caranbirini Waterhole, 16º 16.279 S 136º 0 4.837 E, 6-x-2005. Western Australia. 2/1/1/, Pools upstream of Bell Gorge Falls, The Kimberley, 11-ix-1998; 1/1/5, Lily Creek Lagoon, Kununurra, 15º 46’ S 128º 44’ E, 17-ix- 1998; 1/3/0, Lake Kununurra, 10 km SE of Kununurra, 15º 52’7.45” S 123º 45’46.75” E, 19-ix-1998; 2/3/1, Arthur Creek, at crossing with Great Northern Highway, 23-ix-1998. New South Wales. 0/1/1, Small pools N of Lake Hiawatha, Yuragir NP, 29º 47.315 S 153º 15.171 E, alt. 60 m asl, 10-xi-2003.
Diagnosis. Male genital field bilobated; dorsum with one large plate. Female with a large frontal shield, not incorporating the eyes.
Description. Male: Idiosoma L/W 1769 (1447–1849)/1588 (1307–1668). Dorsum with one large plate, 643 long and 905 wide, incorporating the pre- and postocularia. First, third and fourth coxae with one seta, fourth coxae posteromedially ending in a relatively narrow extension. However, width of this extension variable. Genital field 300 long and 332 wide, anterior margin either straight or indented. Genital field bilobated, anterior and posterior parts separated by a sclerotized bar, but often this bar absent. Anterior parts with numerous acetabula and seven setae, one pair of acetabula distinctly larger than the other acetabula. Posterior part of genital field with numerous setae; posterior margin with a fringe of small setae. Gonopore 72 long, surrounded by a fringe of setae. Length of PI–PV: 186, 146, 203, 81, 34; L/H PIII 3.26. Length of I-leg-4–6: 146, 170, 178. Length of IV-leg-4–6: 348, 356, 243. Third and fourth legs with numerous swimming setae.
Female: Idiosoma L/W 2131(1709–1829) /1889 (1568–1608); integument papillate. Dorsum with one large plate, 810 long and 965 wide, incorporating the pre- and postocularia. First, third and fourth coxae with one seta, fourth coxae posteromedially ending in a relatively wide extension. Genital field 203 long and 348 wide, with numerous acetabula, one pair of acetabula distinctly larger than the other acetabula. Length of PI–PV: 186, 162, 242, 92, 40; L/H PIII 3.78; palp more slender than in male. Length of I-leg-4–6: 146, 178, 227. Length of IV-leg- 4–6: 405, 389, 251. Third and fourth legs with numerous swimming setae. See also Cook (1986), figs. 8–11.
Nymph: Idiosoma L/W 1045–166/985–1106. Dorsal plate consisting of two separate plates.
Etymology. The name refers to the old name of Australia, used for the first time by Abel Tasman in 1644.
Remarks. The female assigned by Lundblad (1947) to H. bilobata Halík must be assigned to the new species, as it has a similarly shaped dorsal plate. The female of H. bilobata is described correctly by Cook (1986). The new species is also described by Cook (1986) as Hydrachna sp., but as he had collected only the female, he left it unnamed.
A more or less similarly shaped dorsal plate can be found in H. similis Cook, 1967, H. similans Marshall, 1928 and H. kloomi Imamura, 1964. The latter two species have a very stocky palp, while H. similis has a non-bloated male genital field. The female of H. mysorensis has also a similar dorsal shield, but with two more small setae. The female of H. triscutata (known from one specimen only) has a dorsal plate which is triangular indented posteriorly. The new species occurs in Western Australia, Northern Territory, Queensland, New South Wales and Victoria.
description: Published as part of Smit, Harry, 2014, Australian water mites of the genus Hydrachna Müller, with the description of five new species (Acari: Hydrachnidia: Hydrachnidae), pp. 170-186 in Zootaxa 3827 (2) on pages 179-181, DOI: 10.11646/zootaxa.3827.2.3, http://zenodo.org/record/225232