英語聽力文摘 變性的青蛙

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Gender-Jumping Toads

美國研究人員說，常用除草劑阿特拉津會令雄蛙變性為雌蛙。美國加利福尼亞大學(xué)伯克利分校研究人員把40只雄性非洲爪蛙放入阿特拉津濃度為10億分之 2.5的水中，發(fā)現(xiàn)90%雌性化，“10%變性成雌蛙，與未接觸阿特拉津的雄蛙交配后產(chǎn)卵”。阿特拉津又名莠去津。先前研究顯示，這種除草劑會干擾激素分泌，導(dǎo)致蛙體同時具備雄性和雌性特征，可能是野生蛙類等兩棲動物數(shù)量下降的一大原因。研究人員蒂龍·海斯說：“我們過去知道，(阿特拉津會導(dǎo)致)雄蛙減少、變得雌雄同體。這項(xiàng)研究明確顯示，(它會使)許多蛙變性。”

As 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.

譯文：

就如你聽說的那樣，青蛙和蟾蜍在過去的數(shù)年中都過得很艱難。

有些種群已經(jīng)完全消失了，有些患上了疾病，有些嚴(yán)重畸形，如多長了或是失去了四肢。現(xiàn)今佛羅里達(dá)大學(xué)科學(xué)家們的研究帶來了更壞的消息，他們發(fā)現(xiàn)生活在農(nóng)田周圍的這些擁有彈簧腿的兩棲雄性動物，極有可能演變生長出雌性性器官，并表現(xiàn)出其它雌性的特征。

是什么樣的農(nóng)田耕作讓青蛙有如此的性別跳躍呢?佛羅里達(dá)大學(xué)的研究人員還不確定，但其中可能的罪魁禍?zhǔn)字痪褪前⑻乩颍环N被種植甘蔗的農(nóng)民廣泛使用的除草劑。其它與農(nóng)田有關(guān)的化學(xué)物質(zhì)也有可能。為了查明引起青蛙和蟾蜍畸形的原因，研究人員從多個地點(diǎn)搜集了樣本。一些青蛙生活在城郊郊發(fā)展地帶，一些生活在農(nóng)田附近。在農(nóng)田周圍搜集的雄性樣本也多半表現(xiàn)出雌性化的跡象。

例如，在大農(nóng)場附近居住的雄性青蛙，百分之四十同時擁有睪丸和卵巢。其余的百分之二十擁有正在進(jìn)化中的畢氏器官 -- 在雄性青蛙體中中并沒有任何功能，但是一旦睪丸停止工作，這個器官就會轉(zhuǎn)變?yōu)槁殉病Ｒ恍┬坌郧嗤鼙话l(fā)現(xiàn)擁有裝滿卵的畢氏器官。問題的一部分就是雌性化的青蛙有可能會不孕。如果沒有陽剛的雄性青蛙，雌性青蛙就會處于孤立無援的境地，青蛙的數(shù)量就會減少。