Sexes May Need Different Dinners

July 17, 2008 -- The wisdom of feeding meat to a man has been thrown into question by a study that shows the secret to a long reproductive life in males -- at least among insects -- is not protein, but carbohydrates.

The study, published today in Current Biology, suggests that it is females who should be pulling out the steak knife to ensure their reproductive fitness.

Lead author and University of New South Wales biologist Alexei Maklakov said his study on Australian black field crickets is the first of its kind to examine the influence of gender in determining which diet is best for long life and breeding success.

Although he found that what's good for the goose isn't necessarily good for the gander, males and females end up eating a compromise diet that is less than optimal for both of them.

For the study, which also involved researchers from the University of Sydney and Massey University in New Zealand, the male and female crickets were fed a range of diets that included different ratios of proteins to carbohydrates.

The researchers then studied the insects' response to the diets in terms of lifespan and reproductive fitness.

For the females this meant once a week counting the number of eggs they laid, and for the males, measuring the number of calling noises they made during the night.

The sexes had very different peaks in respect to reproductive fitness and lifespan under different dietary regimes.

Maklakov, from the Evolution and Ecology Research Center, said reproductive success in female crickets is optimized by a diet with a one-to-one ratio of protein to carbohydrates.

For males, however, reproductive success came with a diet favoring carbohydrates over proteins in an eight-to-one ratio.

Male crickets maximize their reproductive success by calling out to prospective mates throughout the night.

"Males don't need much protein," he said. "They just need energy to basically sit and call out all night."