Fig. 5. Effect of changes in aerial O₂ partial pressure (P_O2,air) on the mean apnoeic O₂ consumption rate (_O2,ap) of Trichogaster leeri. The relationship is described by the logarithmic curve: _O2,ap=–19.2+45.8log(P_O2,air) (r²=0.63, N=2 for 5 kPa and N=6 for 10 kPa as individual breaths were invisible on the others; and N=7 for remaining treatments). Treatments not denoted by the same letter are significantly different. All data are shown as means ± s.e.m.