Sperm competition risk drives plasticity in seminal fluid composition

Area of Science:

• Reproductive biology
• Evolutionary ecology
• Proteomics

Background:

• Ejaculates comprise sperm and seminal fluid proteins vital for male reproductive success, especially under competition.
• Males are hypothesized to adjust ejaculate production based on social cues, particularly sperm competition risk.
• The house mouse (Mus musculus domesticus) serves as a model to investigate ejaculate tailoring to the social environment.

Purpose of the Study:

• To test if males adjust ejaculate composition (sperm and seminal fluid) based on social environment and sperm competition risk.
• To quantitatively analyze seminal fluid proteome composition in relation to sperm competition cues.
• To determine if mating opportunities, distinct from sperm competition risk, influence ejaculate investment.

Main Methods:

• Quantitative proteomics analysis of seminal fluid composition.
• Experimental manipulation of social environment to simulate varying sperm competition risks.
• Measurement of sperm and seminal fluid production in house mice (Mus musculus domesticus).

Main Results:

• Seminal fluid proteome composition significantly differs based on sperm competition risk.
• At least seven of 31 examined seminal fluid proteins showed differential abundance under varying competition levels.
• Proteins like SVS 6, SVS 5, and CEACAM 10 were more abundant in high sperm competition scenarios; total ejaculate investment increased with competition risk.

Conclusions:

• Male ejaculate components, both sperm and seminal fluid, exhibit significant plasticity influenced by the social environment.
• Sperm competition risk is a critical driver of male ejaculate production decisions, including seminal fluid composition.
• The study demonstrates adaptive tailoring of ejaculate traits in response to perceived reproductive challenges.