Mexican scientists have found that male goodeid fishes exposed to insecticides before birth are less attractive to females in later life.
Exposure to low levels of organophosphate insecticides during embryonic development resulted in males with smaller ornamental fins, less intense yellow colour and lower display rates, making them less attractive to females.
Publishing their results in the latest issue of the Proceedings of the Royal Society B: Biological Sciences, Omar Arellano-Aguilar and Constantino Garcia exposed pregnant females of Girardinichthys multiradiatus to low levels of methyl parathion (by soaking their food in a solution containing the insecticide), a highly toxic organophosphate insecticide that is widely used for food crops.
The authors then raised the offspring of both test and control females separately, and carried out mate choice experiments on the male offspring. The authors found that the male offspring of the fish exposed to insecticide were smaller in both body size and relative size of ornamental (dorsal, anal and caudal) fins than the male offspring from the control females.
They also found the insecticide-exposed males to have a less intense yellow colour on the opercula and ornamental fins than on the control males.
Thirdly, the authors found that exposed fish had a more parsimonious courtship style, only rarely performing the seemingly more energetic dances that characterize courtship escalation in this species, and lastly, the authors found that females were less willing to mate with the insecticide-exposed fish than with the control fish (perceiving the former as less attractive).
The authors conclude, our results support the idea that sexual selection can compromise population survival, and that anthropogenic factors may thus disproportionately affect species in which sexual selection is intense.
For more information, see the paper: Arellano-Aguilar, O and CM Garcia (2008) Exposure to pesticides impairs the expression of fish ornaments reducing the availability of attractive males. Proceedings of the Royal Society B. Biological Sciences 275, pp. 1343"1350.