Analysis of total protein extracts at selected stages by Western blot showed that larval haemoglobin was expressed in stage 40 tadpoles but not in stage 46 toadlets (Fig. 1b) . Adult globin protein was first detected in stage 36 tadpoles (faint signal) and continued to increase in abundance after metamorphosis. The positive control used for the experiments was recombinant adult globin that migrates as a larger protein than the native globin on PAGE gels due to the addition of a 6XHis-tag and plasmid linker sequence. The detection system was specific; anti-larval globin antibody detected larval globin, but not recombinant and native adult haemoglobins, and vice versa for the anti-adult globin antibody. Thus we confirmed that the globin switch seen at the mRNA level was also seen at the protein level.