Male fruit flies can smell a good mate based on her metabolism

Different animal species have different criteria for what they find attractive, ranging from color to odor to singing abilities, and many of these traits are linked to good health and fertility. A previous study by the researchers found that male fruit flies tend to prefer females whose insulin signaling causes them to devote more energy to reproduction than to storage and survival. They further investigated this phenomenon by manipulating insulin signaling in different tissues in female fruit flies and then seeing whether male fruit flies found them attractive. Their experiments showed that a female's attractiveness stems from low insulin signaling in their energy storage organ, called the fat body, and high insulin signaling in the follicle cells that support egg production. Signaling in both of these tissues affected the pheromone-producing cells, which altered how attractive the female was perceived. The researchers also found that when they genetically manipulated insulin signaling in a way that made females more attractive, it also caused them to produce more offspring, suggesting that the attractiveness created by insulin regulation is a reliable cue for males looking for highly fertile females.

"This adds to the growing evidence that natural selection has led to perceptive systems that are highly tuned to evaluate aspects of individual fitness," says Fedina.

"We show that even simple animals have evolved the capability of sensing molecular activities that determine reproduction and aging in many species. These cues may have evolved to influence attractiveness because they accurately predict mate fitness," adds study senior author Scott D. Pletcher.

Future studies that can further dissect pathways mediating attractiveness, and also determine how they are influenced by internal conditions and the environment, will help reveal how animals engage in sexual communication.