A male's seminal fluid increases later competitors' productivity

Area of Science:

• Evolutionary Biology
• Reproductive Biology
• Animal Behavior

Background:

• Polyandrous females engage in mating with multiple males, leading to sperm competition.
• Seminal fluid proteins influence male reproductive success by affecting female remating and directly impacting sperm competition.
• The 'second male advantage' describes the phenomenon where the second mating male fathers most offspring.

Purpose of the Study:

• To investigate an additional mechanism by which seminal proteins contribute to the second male advantage.
• To determine how seminal proteins already present in a mated female affect offspring production by subsequent males.

Main Methods:

• Experimental manipulation of seminal proteins in mated females.
• Quantification of offspring production by successive males.
• Analysis of the duration of paternity for each male.

Main Results:

• Seminal proteins from the first male enhanced offspring production by the second male.
• This enhancement was not due to increased female productivity or a general increase in offspring.
• The effect was specifically linked to an extended period of offspring sired by the second male.

Conclusions:

• Seminal proteins from the first male can protect subsequent competitor sperm.
• This protective effect extends the paternity of the second male, contributing to the second male advantage.
• This represents a novel mechanism where seminal proteins confer an advantage to later-arriving sperm.