Sex can directly affect the subsequent behaviour of female fruit flies and how male fruit flies age, according to two separate papers published online in Nature Ecology & Evolution this week.
After mating, females of many species become more aggressive, which may be related to the need to protect their offspring. However, the direct mechanism involved in this increased aggression has remained unknown. Mating also has long-term effects on male physiology and ageing, but, again, the mechanisms are not well understood.
In the first study, Eleanor Bath and colleagues show that some of the increase in aggression that Drosophila melanogaster females show to other females after mating is a direct result of the sex peptide component of sperm, with other sperm proteins also involved. Using genetic mutant females that do not produce eggs, and mutant males that do not produce sperm, the authors were able to disentangle the direct and indirect effects of sperm on female aggression. They find that sperm directly increases aggression towards other females, rather than aggression being a by-product of egg production or the result of the physical act of mating itself.
In the second paper, Scott Pletcher and colleagues investigate the negative effects of exposure to females on male fruit fly lifespan. They used males and females that had been genetically engineered to have the pheromone profile of the opposite sex, along with controls. They find that exposure to the female pheromone reduces male lifespan, but that the act of mating reverses this negative effect.
These two papers illustrate the powerful genetic tools available to researchers for exploring the behavioural and physiological consequences of reproduction with fruit flies. Both sets of authors speculate that similar effects could be found in mammals. In an accompanying News & Views, Mariana Wolfner and Tracey Chapman write: “their (Eleanor Bath and colleagues) results show that aggressive behaviours in one sex can be influenced significantly by chemical messages from the other, and open up many questions regarding the function and adaptive value of female aggressive behavior.”