Owing to its complex composition, the mixture of sperm and seminal fluid substances that comprise an ejaculate has recently been likened to a musical symphony. In a new study I conducted with former colleagues at the University of Liverpool and published this week in BMC Biology, we used proteomics techniques to ask whether male mammals can plastically adjust ejaculate composition. We discovered that the “seminal symphony” males produce indeed depends strongly upon the prevailing “social milieu”. Under more competitive conditions, males produce more sperm and a different blend of seminal fluid proteins than they do under less competitive conditions. This is presumably because high sperm numbers and large amounts of certain seminal fluid proteins enhance male competitive fertilization success, but aren’t needed when there are no competitors around, and so plasticity in ejaculate composition is selectively favoured.
Ramm SA, Edward DA, Claydon AJ, Hammond DE, Brownridge P, Hurst JL, Beynon RJ, Stockley P (2015) Sperm competition risk drives plasticity in seminal fluid composition BMC Biology 13:87. doi: 10.1186/s12915-015-0197-2
Image credit: from Beethoven’s Symphony No. 5. Licensed under Public Domain via Wikimedia Commons.