Fig. 1. Effect of increasing food concentrations on (A) appendage beating rate (fA) and (B) heart rate (fH) of D. magna (2.68±0.22 mm long) at normoxic conditions. Data are given as means ± S.D. (N=4 except for 5.6x10⁴ cells ml^-1, where N=2). A repeated-measures ANOVA was performed for all food levels except 5.6x10⁴ cells ml^-1. Neither the mean fA (F=49.9, groups d.f.=6, remainder d.f.=18, P<0.001) nor the mean fH (F=28.8, groups d.f.=6, remainder d.f.=18, P<0.001) were the same in animals on all seven food levels. The results of multiple comparisons among pairs of means are shown in Table 1.