1. Florida Game and Fresh Water Fish Commission, Wildlife Research Laboratory, 4005 S. Main Street, Gainesville, Florida 32601, USA
2. Present address: U.S. Fish and Wildlife Service, Sheldon-Hart Mountain Refuge Complex, P.O. Box 111, Lakeview, Oregon 97630, USA (e-mail: )
3. Department of Pathobiology, College of Veterinary Medicine, University of Florida, Gainesville, Florida 32611, USA