[1] Univ Otago, Dept Biochem, Dunedin, New Zealand
[2] Univ Cambridge, Dept Zool, Cambridge CB2 3EJ, England
[3] Max Planck Inst Behav Physiol, D-82346 Andechs, Germany
[4] Univ Oxford, John Radcliffe Hosp, Inst Mol Med, MRC,Mol Haematol Unit, Oxford OX3 9DS, England
[5] Monash Univ, Dept Anat, Clayton, Vic 3168, Australia