英语听力文摘 English Digest 286、变性的青蛙

　　Gender¹-Jumping Toads³
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 entirely⁴, 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 killer⁵ used widely by sugar cane⁶ farmers. Other farm-related chemicals could also play a role. In order to probe the possible causes of frog and toad² deformities, the researchers collected specimens⁷ from various sites. Some of the toads lived near suburban⁸ 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 sterile⁹. Without virile¹⁰ male toads, the females are left high and dry, and toad populations dwindle¹¹.
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。

1 gender   

n.（生理上的）性，（名词、代词等的）性

参考例句：

• French differs from English in having gender for all nouns.法语不同于英语，所有的名词都有性。
• Women are sometimes denied opportunities solely because of their gender.妇女有时仅仅因为性别而无法获得种种机会。

2 toad   

n.蟾蜍，癞蛤蟆

参考例句：

• Both the toad and frog are amphibian.蟾蜍和青蛙都是两栖动物。
• Many kinds of toad hibernate in winter.许多种蟾蜍在冬天都会冬眠。

3 toads   

n.蟾蜍，癞蛤蟆( toad的名词复数 )

参考例句：

• All toads blink when they swallow. 所有的癞蛤蟆吞食东西时都会眨眼皮。 来自《简明英汉词典》
• Toads have shorter legs and are generally more clumsy than frogs. 蟾蜍比青蛙脚短，一般说来没有青蛙灵活。 来自辞典例句

4 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。

5 killer   

n.杀人者，杀人犯，杀手，屠杀者

参考例句：

• Heart attacks have become Britain's No.1 killer disease.心脏病已成为英国的头号致命疾病。
• The bulk of the evidence points to him as her killer.大量证据证明是他杀死她的。

6 cane   

n.手杖，细长的茎，藤条；v.以杖击，以藤编制的

参考例句：

• This sugar cane is quite a sweet and juicy.这甘蔗既甜又多汁。
• English schoolmasters used to cane the boys as a punishment.英国小学老师过去常用教鞭打男学生作为惩罚。

7 specimens   

n.样品( specimen的名词复数 )；范例；（化验的）抽样；某种类型的人

参考例句：

• Astronauts have brought back specimens of rock from the moon. 宇航员从月球带回了岩石标本。
• The traveler brought back some specimens of the rocks from the mountains. 那位旅行者从山上带回了一些岩石标本。 来自《简明英汉词典》

8 suburban   

adj.城郊的，在郊区的

参考例句：

• Suburban shopping centers were springing up all over America. 效区的商业中心在美国如雨后春笋般地兴起。
• There's a lot of good things about suburban living.郊区生活是有许多优点。

9 sterile   

adj.不毛的，不孕的，无菌的，枯燥的，贫瘠的

参考例句：

• This top fits over the bottle and keeps the teat sterile.这个盖子严实地盖在奶瓶上，保持奶嘴无菌。
• The farmers turned the sterile land into high fields.农民们把不毛之地变成了高产田。

10 virile   

adj.男性的；有男性生殖力的；有男子气概的；强有力的

参考例句：

• She loved the virile young swimmer.她爱上了那个有男子气概的年轻游泳运动员。
• He wanted his sons to become strong,virile,and athletic like himself.他希望他的儿子们能长得像他一样强壮、阳刚而又健美。

11 dwindle   

v.逐渐变小（或减少）

参考例句：

• The factory's workforce has dwindled from over 4,000 to a few hundred.工厂雇员总数已经从4,000多人减少到几百人。
• He is struggling to come to terms with his dwindling authority.他正努力适应自己权力被削弱这一局面。