Three new hyporheic water mite species from Australia (Acari: Hydrachnidia)

three new hyporheic water mite species are described from Australia, viz. Wandesia minuta, Partidomomonia elongata and Mellamunda tasmanica. With the description of these three species, some 50 hyporheic water mites species are known from Australia. in this paper the first Partidomomonia species for tasmania is described, the third Wandesia species for Australia as well as the second species of the genus Mellamunda.

iNtROduCtiON the Australian water mite fauna is rich in hyporheic species.thus far, 47 species of certain hyporheic origin are known, with four additional species of possible hyporheic origin (Smit 2007).However, this number might increase due to the fact that Cook (1986) described many new species which are a mixture of epigean and hyporheic species.therefore the habitat of quite a number of species is not known with certainty.moreover, many parts of Australia have not been examined for hyporheic water mites.in this paper three new species will be described from tasmania and Victoria.mEtHOdS All material was collected by the author and this is not repeated in the text.the hyporheic water mites were collected with a pump according to Boulton et al (1992).this is an adapted Bou-Rouch pump, but much lighter, and therefore easier to use in the field.One hyporheic species was collected by hand-netting.Abbreviations used: PI-PV = palp segment 1-5; I-leg-4-6 = first leg segments 4-6; tmAG = tasmanian museum and Art Gallery, Hobart; NmV = museum Victoria, melbourne; RmNH = Netherlands Centre for Biodiversity Naturalis, Leiden; NP = National Park; asl = above sea level.

Etymology
Named for its relatively small size.
Remarks thus far, 13 species of the subgenus Pseudowandesia (K.O.Viets 1987; www.watermite.orgviewed on February 1, 2012) are known worldwide.the subgenus has been found in Europe, Argentina, india, Australia and Siberia, including two from Australia: W. glareosa Weigmann &Schminke, 1970 andW. troma Cook, 1986.All known species are much larger (>1400) than the new species described here.the two known Australian species have the fourth coxal plates with a convex medial margin and the medial margin of the third coxal plates is relatively much larger.moreover, W. troma has a slender palp, while the male of W. glareosa has a genital field with two pairs of setal sclerites.
Although the holotype has not been collected with a groundwater pump, it is certainly of hyporheic origin.most wandesiine species live in interstitial habitats (Cook 1974).Under large stones one can find smallscale exchange of the stream and the hyporheic zone (Boulton et al 2010).
Family momoniidae K. Viets Genus Partidomomonia Cook, 1983 thus far, four Partidomomonia species are known, one from New Zealand (Cook 1983) and three from Australia (Harvey 1990;Smit 2007).the Australian species were reported from Victoria (two species) and Queensland (one species).The first species from Tasmania is described below.

Diagnosis
idiosoma elongated, distance of anterior pair of acetabula and central pair of acetabula larger than distance between two posterior pairs, PiV stocky, i-leg-5 and -6 slender.

Etymology
Named for the elongated idiosoma.
Remarks the new species is close to Partidomomonia blythi Harvey, 1990 (in parentheses data of P. blythi), but dif-fers in its larger size (less than 450), the configuration on the acetabula (acetabula equidistant from each other) and i-leg-5 longer than i-leg-6 (same length).Both P. cabanandra Harvey, 1990 andP. tertia Smit, 2007 have a slender PiV and a less elongated idiosoma shape, while in P. tertia the lateroglandularia 5 are fused with the large posterior dorsal plate (free in the new species).
Family Athienemanniidae K. Viets Subfamily Notomundamellinae Cook Mellamunda Harvey, 1988 Revised diagnosis Male genital field with 5-6 acetabula lying in the gonopore and 3-9 acetabula fused with the ventral shield.Eyes not lying in capsules but below the integument.See further Harvey (1988).IV-leg not or slightly modified.

Diagnosis
Male genital field with six pairs of acetabula lying in the gonopore and three pairs fused with the ventral shield.

Description
male: idiosoma brownish, dorsal and ventral shields present.Ventrum 640 long, dorsum 640 long, width of idiosoma 397.dorsal shield complete, 518 long and 348 wide, with three pairs of glandularia.Eyes not in capsules but lying below the integument.First coxal plates extending beyond anterior idiosoma margin.Suture lines of coxae indistinct, lateral suture lines obsolete.First and second coxae fused, third and fourth coxae medially close to each other.Genital field with six pairs of acetabula lying in the gonopore and three pairs of acetabula fused with the ventral shield.Ventroglandularia 2 absent, only accompanying seta present.Lengths of 74,48,78,32.Pii with three setae in anterodorsal corner, Piii with a long seta on medial side, PiV rotated (and therefore not completely visible in illustrations) with one very long seta and one shorter seta, PV blunt.Lengths of i-leg-4-6: 86, 120, 108; i-leg-5 ventrally with two long, thin setae.Lengths of iii-leg-3-6: 62, 80, 116, 96; iii-leg-3 and -4 expanded ventrally, latter segment with two stout setae and one hyaline spatulate seta.Lengths of iV-leg-5-6: 176, 154.Legs without swimming setae, although iV-leg-5 and -6 ventrally with 4-6 long, thin setae.

Etymology
Named for its occurrence on tasmania.
Remarks this is the second species of the genus, the other one is M. acares Harvey, 1988.the new species differs from the latter in the number of acetabula, five acetabula lying in the gonopore and nine acetabula fused with the ventral shield in M. acares.moreover, the shape of the ventral expansion of iii-leg-4 is different in M. acares (more angular), and so is the shape of the setae of this extension (compare fig. 25 of Harvey 1988 with fig.16).Although the new species was collected with a groundwater pump, the presence of eyes and coloration might indicate that it is an epigean species.