Males and females pursue different reproductive strategies, which often bring them into conflict— many traits exist that benefit one sex at a cost to another. Decreased female survival following mating dramatically demonstrates one aspect of this phenomenon. Particularly intriguing is the evidence that secreted compounds can shorten lifespan of members of the opposite sex even without copulation taking place. The purpose of such signals is not clear, however. While it is possible that they could limit subsequent mating with competitors or hasten post-reproductive demise, thus decreasing competition for resources, they are also likely to harm unmated individuals. Why would a system exist that reduces the vigor of potential mates prior to mating?
Key results
- Male-secreted signals increased the number of progeny produced by mated hermaphrodites (who are essentially equivalent to females). One aspect of the improved reproductive function in hermaphrodites is the increase in the number of germline progenitor cells, a population from which oocytes are derived.
- The salubrious effects of the male-secreted signals on the health of the hermaphrodite germline are mediated by an ascaroside pheromone, ascr#10.
- Contrary to their beneficial effects on the hermaphrodite germline, ascaroside pheromones shorten hermaphrodite lifespan.
- Males also produce a signal, which is not mediated by an ascaroside, that hastens hermaphrodite development, particularly the onset of adulthood.
- Both the ascaroside and the novel non-ascaroside signals are conserved.
- Sterile males cease to produce the signal that benefits the hermaphrodite germline, but continue to secrete the signal that accelerates reproductive development.
Conclusions
- Males produce molecules that affect hermaphrodite germline (ascarosides) and somatic development (non-ascarosides). These signals manipulate hermaphrodite/female reproductive physiology in favor of the germline at the expense of the soma.
- The male signals benefit hermaphrodite reproduction, but also shorten the lifespan. This likely represents ‘‘collateral harm’’, because the negative side effects are not the goal, but rather inadvertent consequences of an effort to manipulate physiology. The tangible reproductive benefits come with enhanced aging that occurs well after the end of the reproductive period.