Competing for a mate impacts sperm quality and performance
If multiple males are competing for a mate, it impacts the quality performance of sperm.
Rival males have better-performing sperm that’s faster and more efficient but also more susceptible to DNA damage, according to a new zebrafish study conducted by researchers from the University of Alicante and the University of Uppsala in Sweden.
In the study, published in the journal Evolutionary Biology, the researchers compared the sperm of two male zebrafish in the presence of a single female to the sperm of a single male in a tank with two females.
The fish were observed and monitored for two weeks, and the researchers used geometric morphometry to analyze and compare differences in sperm shape, size, quality, and performance.
The two rival males developed competitive spermatozoa that were faster, had smaller heads, and were more efficient compared to the single male fish with no competition.
The competing spermatozoa showed higher rates of DNA damage and the researchers say this could impact not only fertilization but also future offspring.
A potential explanation for the higher rates of damage in the competing males is that sexual rivalry increases stress levels.
Sexual rivalry and sperm design are not well understood, and studies like this can help shed insight on how competition among males impacts evolution and species diversification.