英语听力文摘 变性的青蛙
Gender-Jumping Toads
美国研究人员说，常用除草剂阿特拉津会令雄蛙变性为雌蛙。美国加利福尼亚大学伯克利分校研究人员把40只雄性非洲爪蛙放入阿特拉津浓度为10亿分之 2.5的水中，发现90%雌性化，“10%变性成雌蛙，与未接触阿特拉津的雄蛙交配后产卵”。阿特拉津又名莠去津。先前研究显示，这种除草剂会干扰激素分泌，导致蛙体同时具备雄性和雌性特征，可能是野生蛙类等两栖动物数量下降的一大原因。研究人员蒂龙·海斯说：“我们过去知道，(阿特拉津会导致)雄蛙减少、变得雌雄同体。这项研究明确显示，(它会使)许多蛙变性。”
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.
译文：
就如你听说的那样，青蛙和蟾蜍在过去的数年中都过得很艰难。
有些种群已经完全消失了，有些患上了疾病，有些严重畸形，如多长了或是失去了四肢。现今佛罗里达大学科学家们的研究带来了更坏的消息，他们发现生活在农田周围的这些拥有弹簧腿的两栖雄性动物，极有可能演变生长出雌性性器官，并表现出其它雌性的特征。
是什么样的农田耕作让青蛙有如此的性别跳跃呢?佛罗里达大学的研究人员还不确定，但其中可能的罪魁祸首之一就是阿特拉津，一种被种植甘蔗的农民广泛使用的除草剂。其它与农田有关的化学物质也有可能。为了查明引起青蛙和蟾蜍畸形的原因，研究人员从多个地点搜集了样本。一些青蛙生活在城郊郊发展地带，一些生活在农田附近。在农田周围搜集的雄性样本也多半表现出雌性化的迹象。
例如，在大农场附近居住的雄性青蛙，百分之四十同时拥有睾丸和卵巢。其余的百分之二十拥有正在进化中的毕氏器官 -- 在雄性青蛙体中中并没有任何功能，但是一旦睾丸停止工作，这个器官就会转变为卵巢。一些雄性青蛙被发现拥有装满卵的毕氏器官。问题的一部分就是雌性化的青蛙有可能会不孕。如果没有阳刚的雄性青蛙，雌性青蛙就会处于孤立无援的境地，青蛙的数量就会减少。
