Female fish choose well fed males over undernourished ones: Study

By Dr. Ananya Mandal, MDJan 12 2012

At least in some species being well fed as a kid makes a male more attractive to the opposite sex. Researchers from the Australian National University (ANU) have discovered female mosquitofish (Gambusia holbrooki) prefer males with a strong nutritional upbringing. The preference is there even when the males are otherwise identical to previously undernourished fish. These mosquitofish were introduced to Australia in an attempt to control mosquitoes.

Research author Andrew Kahn, who is a PhD student at ANU's Research School of Biology, says males which are similar in body size, but have a different developmental history, are not equally attractive to females. “We gave female fish a choice between two full brothers who were born on the same day,” Mr Kahn said in a statement. “One brother grew normally and the other had a period of poor nutrition and compensated for it by accelerating growth and delaying maturation. The really interesting thing was that females seemed to be able to tell the difference between them.” The study has been published in the online journal Biology Letters.

Mr Kahn explained well-fed males were attractive to females because they would be less susceptible to diseases. Also, by choosing a male with a better development history, any offspring were more likely to be good at getting food when they bore young. “This work demonstrates there are hidden costs to a poor start in life,” Mr Kahn said.

Green swordtails which are from the same family of fish, are more dominant if they develop normally, says Andrew, who speculates that this might be one way females identify well-fed males. “However [unlike green swordtails] there is no active courtship between male and female mosquitofish, it's more a matter of time and place,” he told Australian Geographic. “The females just seem to like hanging out with the well-fed males more.”

Jules Livingston, an ANU honors student and co-author of the paper, previously showed that juvenile mosquitofish born into a food-scarce environment will undergo accelerated growth when food becomes available and delay sexual maturation to catch up with well-fed males of the same age.