The relationship of body condition, superoxide dismutase, and superoxide with sperm performance

Sperm competition theory predicts a negative correlation between somatic investment in traits that aid in pre- and postcopulatory sexual selection. Sperm performance is critical for postcopulatory success but are susceptible to damage by free radicals such as superoxide radicals generated during mitochondrial respiration (mtSOx). Males can ameliorate damage to spermatozoa by investing in the production of antioxidants, like superoxide dismutase (SOD), which may act as a mechanistic link for pre and postcopulatory trade-offs. Some male Australian, colour-polymorphic painted dragon lizards (Ctenophorus pictus) possess a yellow throat patch (bib) that females prefer over non-bibbed males and are also more likely to win male-male contests indicating that males with bibs are better at monopolizing females. We tested whether the sperm performance in non-bibbed males was superior to that of bibbed males as predicted by sperm competition theory. We show that blood cell mtSOx levels are negativ...