Fig. 5. Calibration of Oxyphor R2 in the haemolymph of D. magna. The data show the reciprocal of the phosphorescence lifetime plotted against oxygen partial pressure P_O2. (A) Comparison of individual calibrations in Hb-poor (open circles, N=3) and Hb-rich haemolymph (filled triangles, N=3). Individual calibrations were analyzed by linear regression analysis using the Stern–Volmer equation (Equation 2) and the regression parameters averaged to obtain a mean regression line (broken line). (B) Pooled data (means ± S.D., N=7) of further calibrations with Hb-poor and Hb-rich haemolymph. The linear regression line (broken line) was used to convert in vivo phosphorescence lifetime images into P_O2 images.