Mass-specific metabolic rate and sperm parameters in eutherian mammals.
Relationships between mass-specific metabolic rate (ml O2 h-1 g-1) and (A) sperm straight-line velocity (μm s-1), (B) total sperm length (μm), and (C) sperm straight-line velocity (μm s-1) after controlling for the effect of total sperm length (μm), in mammalian species. All variables were log10-transformed. Figure points in (A) and (B) represent data values. Figure points in (C) are partial residuals estimated from a regression between sperm straight-line velocity and total sperm length (Y-axis), and from a regression between mass-specific metabolic rate and total sperm length (X-axis). R2 and p-values were estimated using phylogenetically controlled regression analyses (PGLS).