• ‘good genes’ hypothesis;
  • fish;
  • offspring viability;
  • parasitism;
  • sexual selection


According to the ‘good genes’ hypothesis, sexual ornaments provide an indication of the ‘quality’ of the bearer. In roach, Rutilus rutilus, breeding tubercles (BTs) may signal resistance against the digenean parasite, Rhipidocotyle campanula. Life history theory predicts that there should be a trade-off between parasite resistance and other life history traits. In roach, this could imply a trade-off between parasite resistance in mature fish and some larval feature. We studied embryo survival and the early viability of larvae of male roach in relation to expression of BTs and parasite resistance in maternal half-sibling families. Highly ornamented males had higher resistance against R. campanula than less ornamented males, but the BTs were not related to either embryo survival or larval viability. However, sires having higher resistance to R. campanula had lower larval viability. These results suggest that BTs of male roach do not indicate ‘quality’ in terms of early survival or viability, but rather in terms of adult parasite resistance.