1. School of Biological Sciences; Flinders University; Adelaide SA 5042 Australia
2. Museum and Art Gallery of the Northern Territory; P.O. Box 4646 Darwin NT 0801 Australia
3. Inland Waters and Catchment Ecology Program; SARDI Aquatic Sciences; P.O. Box 120 Henley Beach SA 5022 Australia
4. Pontificia Universidade Catolica de Minas Gerais; Belo Horizonte MG 30535-610 Brazil