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Of Uranium Mines and Freshwater Isopod Crustaceans


Over the last 20 years, the Environmental Research Institute of the Supervising Scientist (ERISS, Federal Department of the Environment) has been monitoring freshwaters around Kakadu National Park. The overall aim of their work is environmental due diligence related to uranium mining within the national park boundaries. One of the project ecologists, Chris Humphrey and colleagues collected invertebrates from numerous streams arising in the 'stone country' on the western margin of the Arnhem Plateau in Australia's Northern Territory. At certain times of the year, they found isopod crustaceans in the genus Eophreatoicus (order Phreatoicidea). These isopods live in springs at the base of the Arnhem Plateau and come out into the streams during the summer wet season. As the dry season commences in late summer and stream flows recede, they move back upstream to their springs and, if necessary, burrow underground until the next wet. In the 1990s, Buz Wilson and Winston Ponder visited the park and collected a few large samples of these animals, and provided ERISS with preliminary identifications. Buz has been studying the Phreatoicidea for over a decade, and is preparing a large monograph on all Australian genera, so these Kakadu isopods were of substantial interest. Chris has been sending Eophreatoicus specimens to Buz since that initial visit, and in 2004 they successfully applied for an ABRS grant to describe the species, which they thought amounted to around 10 species. This new project was a bit like opening "Pandora's box" because Buz's laboratory study uncovered at least 30 new species. These morphological discoveries were subsequently confirmed by genetic research done in the Australian Museum's DNA lab, with the assistance of Don Colgan, Karen Gray and Rebecca Johnson. One surprising discovery was a cluster of distinct morphological species in the vicinity of Jabiluka, one of the sites proposed for mining uranium: 13 species were found within less than 10 km of the Jabiluka Outlier, with 2 or 3 species at each site. This paper is now published: "The Eophreatoicus Nicholls, 1926 species flock from Kakadu and Arnhem Land, with a description of a new genus of Amphisopidae (Crustacea : Isopoda : Phreatoicidea)" Zootaxa 4854(1): 1-303.

Aerial photograph of the rugged landscape surrounding Ngarradj Creek (westward view)in a region including the Jabiluka outlier and the northwestern margin of the Arnhem Plateau. The inset shows seven new species of Eophreatoicus (clockwise from top), all found within a radius of 8.3 kilometers in this region: E. warnbi, E. mawoenewoene, E. kudjaldordo, E. ngarradj, E. boywek, E. binjdjarrang and E. djurrukunja. (credits: Mike Saynor, Lisa Chandler)

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