英語(yǔ)時(shí)差：性別跳躍蟾蜍

Os you may have heard, frogs and toads have had a rough time over the past several years. Some populations have vanished entirely, while others suffer disease and gross deformities like extra or missing limbs.

And now there's more bad news for the spring-legged amphibians---male toads living near farms are likely to develop female sex organs and other female features, according to scientists at the University of Florida.

What is it about farming that causes toads to gender jump? The Florida researchers aren't certain, but one likely culprit is atrazine, a weed killer used widely by sugar cane farmers. Other farm-related chemicals could also play a role.

In order to probe the possible causes of frog and toad deformities, the researchers collected specimens from various sites. Some of the toads lived near suburban development, some near farms. The male specimens collected near farms were most likely to show signs of feminization.

For example, of the male toads living near large farms, forty-percent had both testes and ovaries. Another twenty-percent of these toads had a developing Bidder's organ---an organ that's normally without function in male toads, but that can change into an ovary if the testes stop working. Some of the male toads were found with Bidder's organs full of eggs.

Part of the problem is that the feminized toads are most likely sterile. Without virile male toads, the females are left high and dry, and toad populations dwindle.