Sperm competition and the evolution of sperm metabolism in muroid rodents

TOURMENTE, MAXIMILIANO; VILLAR-MOYA, PILAR; RIAL, EDUARDO; ROLDAN, EDUARDO R. S.

Holderness

Conferencia; Gordon Research Conference: Fertilization & Activation of Development; 2013

Gordon Research Conferences

Sperm competition often leads to increases in sperm numbers and sperm quality, and its effects on sperm function are now beginning to emerge. Rapid swimming speeds are crucial for mammalian spermatozoa, since they need to overcome physical barriers in the female tract, reach the ovum and generate force to penetrate its vestments. Faster velocities associate with high sperm competition levels in many taxa and may be due to increases in sperm dimensions. However, they may also relate to higher ATP content, which can be produced by glycolysis and/or oxidative phosphorylation. First, we examined if variation in sperm ATP levels among species relates to both sperm competition and sperm swimming speed in rodents. We found that sperm competition is associated with variations in sperm ATP content and sperm-size adjusted ATP concentrations between species, which suggests proportionally higher ATP content in response to sperm competition. Moreover, both measures were associated with sperm swimming velocities. Second, we evaluated if differences in sperm ATP content among species were related to variations in the relative contribution of glycolysis and oxidative phosphorylation. Sperm competition was found to be associated to proportionately higher oxidative phosphorylation in relation to glycolysis. Overall, our findings support the idea that sperm competition may select for higher ATP content, which leads to faster sperm swimming velocity, by promoting changes in the relative contribution of ATP-generating pathways.