What's New

eriss isopod expedition: Eophreatoicus kershawi re-discovered!

Chris Humphrey, Don Elphick and John Lowry of the Environmental Research Institute of the Supervising Scientist returned from a short but successful mission to collect type specimens of Eophreatoicus , the genus of isopod that is abundant throughout interstitial waters, and surface seeps and springs of sandstone country of Kakadu and Arnhem Land (including the Jabiluka region). This work is part of an ERISS Landscape project on 'significant species' of Kakadu National Park and originated from an ISP/IUCN request to determine the conservation significance of aquatic crustaceans found in streams adjacent to the Jabiluka mine site.

The isopod component of the study is being conducted in collaboration with Dr George Wilson of the Australian Museum. The Museum will undertake molecular genetics work using funds it and eriss successfully sought from the Australian Biological Resources Study (part of Department of the Environment and Heritage). The results of these genetic studies will contribute to formal taxonomic descriptions of the Eophreatoicus 'flock'.

To date, only one species of Eophreatoicus , E. kershawi , has been described (the 'type' species). Specimens of this species were collected in 1915 by an intrepid ornithologist (a fascinating diary record of his expedition is available), from a sandstone outlier directly north and west of the King River estuary in western Arnhem Land. Since then, eriss , the Australian Museum and other workers have discovered an additional 20 or so species that await formal taxonomic description. The original E. kershawi material was not preserved in a medium suitable for molecular genetics and because the taxonomy and phylogeny of the group is not complete without the type species, it was important to re-collect specimens of E. kershawi .

The King River has a small catchment near the coast in roughly the same longitude as Nabarlek. It is reached about 40 km east off the Murganella Road north of Gunbalanya. The trip in took 7 hours, four of which were spent on the last 10 km of the journey clearing the disused track.

The time of sampling - November - coincided with the time at which the original 1915 collection was made; typically, after the first early storms of the season, isopods become very active and 'mill' en masse in any surface seep or spring emanating from rock crevices. Unfortunately for the eriss team, no rain had fallen at all in the area, which made it difficult finding any free waters in the oppressive 40°C+ heat. Nevertheless, after a 2-km walk, a likely looking crevice was found surrounded by ferns and figs, at the base of an impressive cliff face (see picture below - left). The crevice retreats back some 30 m (see picture below - right).

After discovering and 'bottling' some freshwater crabs, found in moist sand beneath large cobbles at the entrance to the crevice (probably a new species), the team then discovered some small shallow pools in the narrow recesses at the back of the crevice. On all fours and using John's head lamp, the team leader found and bottled . Eophreatoicus kershawi , ~25 specimens!

Additional searches around the (6 x 3 km) outlier found no additional seeps of any significance. All in all, it was a fascinating trip.