Variation in sperm traits is widely documented both at inter-and intraspecific level. However,
sperm traits vary also between ejaculates of the same male, due for example, to fluctuations
in female availability. Variability in the opportunities to mate can indeed have important
consequences for sperm traits, as it determines how often sperm are used, and thus the rate
at which they are produced and how long they are stored before the mating. While being
stored within males' bodies, sperm are subjected to ageing due to oxidative stress. Sperm …