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Aging happens faster when more females are near

A male fly is shown in the foreground facing the camera with an unfocused female fly in the background.
[Image courtesy of Christi Gendron]

Being surrounded by too many females can cause males to age faster, a new study shows.

Historically, scientists haven't looked too closely at how a male’s health or lifespan changes if he senses the presence of a female, or vice versa. But now a study by University of Michigan’s Christi M. Gendron and colleagues published in the 29 November issue of the journal Science does just that.

Gendron and colleagues focused on Drosophila flies -- often called fruit flies. Drosophila males know if females are near through chemical signals females give off called pheromones.

Gendron and her team tested whether changes in female pheromone exposure influenced the lifespan of male flies. To do this, they housed regular flies with flies engineered to express male and female pheromones at different levels. The flies clued into each other’s chemical signals.

When male flies were exposed to female pheromones (through receptors in their legs), they experienced negative health effects -- including reduced amounts of the fat, or energy, they need to survive. Ultimately, these males died sooner, too.

Interestingly, at the same time the males were sensing female pheromones, neurons in their brain related to reward fired, perhaps stimulated at the thought of an opportunity to mate, an important part of the fly life cycle.

Mating never came to pass for some males, and in this population, the negative health effects persisted.

However, in those flies that did get to mate, fat stores were buoyed and lifespans lengthened. This suggests that when sensory expectations tell the brain one thing, but life circumstances present another, aging may not happen in the healthy, expected way – but instead much faster. It hints that a neural circuit in the brain linked to reward may play a role in aging in flies.