SYDNEY, AUSTRALIA -- Fit, well-fed male field crickets die young because they spend too much time courting members of the opposite sex, according to research by Australian scientists in the latest edition of Nature.
The results reveal how male crickets (Teleogryllus commodus) fed on a high protein diet engaged in more "sexual calling" and died sooner than males reared on a low protein diet. The well-fed males also died earlier than well-fed female crickets (females don't "call" to males).
The scientists manipulated the crickets' dietary intake by feeding high, medium and low protein diets to three different groups.
"The high protein fed male crickets spent the extra capital that they got from a better diet on mating behaviour, which shortened their longevity," says Dr Luc Bussiere, a UNSW postdoctoral research fellow and co-author to the study. "So it's obvious that for these crickets, a long life isn't all it's cracked up to be."
"Supporting the idea that well-fed crickets reduced longevity was a consequence of heightened sexual display ("calling)" was the finding that males raised on both high and medium protein diets lost a greater proportion of their body weight after each night's "calling" than those fed on a low protein diet," says UNSW's Dr John Hunt, an ARC postdoctoral research fellow.
Further, despite dying earlier than males fed on a low protein diet, well-fed males "called" more over the course of their shortened lifetime compared to males fed on a low protein diet.
Moreover, males fed on high and medium diets tended to lose weight soon after they commenced their calling behaviour, whereas those on low protein diets tended to delay their calling until later in adult life, thereby enabling them to gain or maintain their body weight for longer.
"One thing that consistently prolongs lifespan in a range of species is a restricted diet. Now we know a bit more about how this occurs in male crickets – by suppressing sexual advertisement," says UNSW co-author, Dr Rob Brooks.
According to UNSW co-author, Dr Bussiere, the best predictor of male mating success in Teleogryllus commodus is the quantity of time spent calling females.
"We heightened this behaviour by manipulating dietary intake. For males on high protein diets it had the effect of promoting their promiscuity and reducing their longevity. They literally knocked themselves out trying to impress female crickets," he says.
"For humans this might seems counterproductive because we don't want to die young – we want to live long lives. But for animals the goal isn't living longer – it's to reproduce."
Drs John Hunt and Rob Brooks were funded by an Australian Research Council grant. Dr Bussiere was funded by a Natural Sciences and Engineering Research Council Fellowship (Canada).
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