549 Journal of the Royal Society of Western Australia, 94: 549–555, 2011 © Royal Society of Western Australia 2011 Aquatic invertebrates of rockholes in the south-east of Western Australia I A E Bayly 1,2 , S A Halse 3 & B V Timms 4 1 School of Biological Sciences, Monash University, Melbourne, Vic., 3800 2 Address for correspondence: 501 Killiecrankie Road, Killiecrankie, Flinders Island, Tas., 7255  iaebayly@activ8.net.au 3 Bennelongia Pty Ltd, 5 Bishop Street, Jolimont, WA, 6014  stuart.halse@bennelongia.com.au 4 Australian Wetlands & Rivers Centre, University of NSW, Kensington, NSW, 2052  brian.timms@unsw.edu.au Manuscript received March 2011; accepted October 2011 Abstract Twelve fooded rockholes located to the east of the Yilgarn Craton, in the Western Australian sector of the Great Victoria Desert, were sampled for aquatic invertebrates. The fauna was depauperate in comparison with that of pan gnammas on the Yilgarn Craton. Only three crustacean species (Lynceus sp. nov., Moina australiensis and Sarscypridopsis sp. nov.) and one insect family (Culicidae) occurred in more than half of the rockholes. Although deep rockholes like pit and pipe gnammas typically have a longer hydroperiod than pan gnammas they have few, mainly eurytopic, species. Keywords: Great Victoria Desert, Ofcer Basin, rock pool, gnamma, Lynceus, Moina australiensis, Sarscypridopsis, Culicidae by chemical weathering. Despite the fact that chemical weathering is generally more potent than physical weathering (Twidale & Campbell 2005), some rockholes are formed wholly or mainly by physical processes such as thermal expansion, frost riving, growth of crystals or pressure release. Such processes commonly result in the shatering of rocks. Silcock (2009) treats rockholes in the sandstone ranges of the Lake Eyre Basin as the product of fracturing followed by the scouring out of rock fragments by running water. Rockholes produced by physical processes generally have sharp, angular surfaces in contrast to the more smoothly rounded features that are so characteristic of true gnammas. While most of the rockholes encountered in this study are gnammas in the sense of Twidale and Corbin, albeit of the non-granite variety, some are not because they were judged as being produced mainly by physical processes. In summary, all gnammas are rockholes but not all rockholes are gnammas. A further point is that most deep gnammas on non-granite substrata such as the laterites that dominate the so-called “breakaway” country in Western Australia are morphologically quite different from those on granite. Unlike the pit gnammas on granite, almost all of which are basin-shaped, many of the deep non-granite gnammas are tube-like or cylindrical with vertical sides and fat botoms. Timms (in manuscript) has distinguished these by the new name “pipe gnammas”. This new term applies to a subset of what, in more general terms, may be called “cylindrical gnammas”. Also included in this study are two rather squarish, rock-floored basins surrounded by rock on three sides but dammed by a ridge of sof sediments on the fourth. These may be plunge pools of systems that are intermitently lotic afer occasional heavy rain (but this is not certain) and are referred to as “waterholes” rather than “rockholes” in Table 1, but the title and text of Introduction If we consider that part of Western Australia south of latitude 26°S, it consists of two major geological regions: that to the west of longitude 123° 30'E (say west of Yamarna) is occupied mainly by the Yilgarn Craton consisting chiefy of Achaean granites, and that to the east of this line (the Eucla and Ofcer Basins) of largely non-granite rocks of lesser age (Fig. 1). Much of the later region was subject to extensive marine inundation in the Early Cretaceous around 120–100 Ma BP and a lesser marine fooding in the Eocene from about 52–37 Ma BP (BMR Palaeo-geographic Group 1990), but most of the Yilgarn Craton escaped these floodings. The Yilgarn region is studded with hundreds of granite inselbergs on the surface of which chemical weathering has etched out thousands of gnammas or rockholes. Either intermitently or episodically these gnammas are flled with rainwater and provide habitat for a surprisingly diverse assemblage of aquatic invertebrates. The nature of this assemblage for the Yilgarn region has received considerable atention during the past two decades and is now relatively well known (see, e.g., Bayly 1997; Pinder et al. 2000; Timms 2006; Jocqué et al. 2007). In contrast, the aquatic fauna of rockholes in the south-east of Western Australia, those to the east of the Yamarna-Balladonia line, has been almost totally neglected. The word “gnamma” comes from the Nyungar language and refers to a rockhole, especially one capable of holding water, and is now frmly established in the anthropological, biological and geological literature. Following the seminal paper of Twidale & Corbin (1963) a gnamma is a rockhole that has been produced