Figure 4. Comparison of the intraspecific metabolic scaling
with body mass in ectothermic vertebrates. Left panels show scaling
regressions performed at various temperatures in inactive individuals of
water- (A ) and air-breathers (B ). Right panels show
regressions for individuals under different activity levels of water-
(C ) and air-breathers (D ), adjusted to the approximate
mean temperature of each dataset (Appendix S8). Dashed lines denote the
upper and lower metabolic scaling slopes (b ) as metabolic level
(L ) increases with temperature (A, B) or activity (C, D). These
slopes were predicted through model estimates, by using values of the
minimal and maximal L values calculated at the geometric
mass-midpoint of the range reported for water- and air-breathing species
in each dataset. B and C show mean b and L values, as the
estimated change in b overlapped 0, indicating no overall effect
of L . The explanation
proposed here for these changes in b is shown on each panel.