Sperm Competition

• Sperm competition is the competition between ejaculates of different males for fertilisation of an ova before and after copulation
• A male can win a sperm competition by stopping others from mating, destroying/removing other sperm, being more attractive, mating more than other males
• In the presence of competition, flies can double their sperm count, and humans have more sperm count when the last time copulated with partner is longer
• Sperm displacement is shown in humans with kamikaze sperm and vacuum removal (thrusting)
• Copulatory plugs are gelatinous plugs left after mating to stop female mating until it dissolves, some species are capable of removing other male's plugs
• Males have 2 types of sperm: aupyrene (fertile) and apyrene, 90% of sperm apyrene and can delay remating as they provide nutrients for female and are less likely to mate again
• Females benefit from multiple matings by gaining spermatophore nutrients, nuptial matings, possible parental care, reduced harrassment, and genetic diversity through cryptic female choice
• Success of sperm is in favour of ejaculate of unrelated males - if two related males mated with same female egg hatching is reduced due to inbreeding