Sexes need different dinners, says study
Dani Cooper
ABC Australia
16 July 2008
The wisdom of feeding the man meat has been thrown into question by a study that shows the secret to a long reproductive life in males is carbohydrates.
A study, published today in Current Biology, suggests 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, Dr Alexei Maklakov, says 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.
And Maklakov says although 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 includes researchers from the University of Sydney and Massey University in New Zealand, the male and female crickets were fed a range of different diets that included different ratios of proteins to carbohydrates.
The researchers then studied the insects' response to the diets in terms of life span and reproductive fitness.
For the females this meant once a week counting the number of eggs they laid and for the males measuring the amount of calling noises they made during the night.
Optimised reproductive success
He says they found the sexes had very different peaks in respect to reproductive fitness and life span under different dietary regimes.
Maklakov, from the Evolution and Ecology Research Centre says reproductive success in female crickets is optimised by a diet with a one to one ratio of protein to carbohydrates.
However for males, reproductive success came with a diet favouring carbohydrates over proteins in an eight to one ratio.
He says male crickets maximise their reproductive success by calling out to prospective mates throughout the night.
"Males don't need much protein," he says. "They just need energy to basically sit and call out all night."
The researchers then studied what the crickets would eat when given a choice in diet.
They found however, that instead of selecting food in a sex-specific manner, males and females ate a "compromise" diet that benefited neither one.
"It is rather surprising because they are not doing what they are supposed to do," Maklakov says.
Sexual conflict
"In crickets males and females do not seem to be able to fully resolve the sexual conflict over what to eat."
For the females the compromise is costly resulting in a 30% reduction in egg production, he says.
The researchers believe the compromise is due to the failure of some gender-dependent traits to evolve.
Because the sexes share most of their genes this can constrain the evolution of sex differences in traits as the same genes in both sexes are likely to be responsible for trait expression.
Evolution and Ecology Research Centre director associate professor Rob Brooks says the results show more attention needs to be given to individual's diets in terms of their sex and reproductive stage.
"It underlines the important lesson that what we want to eat, or if you like, are programmed to eat, is not necessarily best for us," Brook says.
Ramifications
The co-author says although humans and crickets are completely different organisms, the study does have ramifications.
"It's the first time this kind of [gender difference in diet] has been shown," he says.
"Humans are even more fundamentally different between males and females than crickets are.
"In human reproduction the men's role is relatively trivial [while] for women bringing a baby safely to term requires tremendous amounts of energy and diet is very important.
"What men and women need to eat might be more dramatically different than we had realised. However men and women eat very similar diets and our results suggest our tastes and food preferences could be a shared compromise as they are in crickets."
Source:
http://www.abc.net.au/science/artic...ce&topic=latest
Sexes need different dinners, says study
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