Virgin Births in Snakes Shock Scientists|蛇类处女产子震惊科学家

Virgin Births in Snakes Shock Scientists

by Brian Foden

Asexual reproduction has become more frequent in nature.

　　Researchers in the United States have discovered something that has shocked them about snakes in the wild. At least some females are capable _(1)_ giving birth without any help from males. After capturing dozens of pregnant copperhead and cottonmouth female pit vipers in their natural environments, researchers were _(2)_ to have discovered two cases of virgin births. The scientists figured _(3)_ that no males were involved in the reproduction. This is because all the genetic material of the two offspring came from the mothers. Based on this study, researchers _(4)_ that 2.5 to five percent of snake litters could be the result of this type of asexual reproduction, which is also known as parthenogenesis (单性生殖).

　　While virgin births are fairly _(5)_ in some invertebrates, such as ants and bees, they are rare in vertebrates like snakes. There had _(6)_ been isolated cases of vertebrates giving birth via parthenogenesis while in captivity. Some examples of these rare births include snakes, sharks, lizards, and even some species of birds. However, in all of these cases, asexual reproduction occurred while the creatures were removed from their natural habitats and _(7)_ separated from males.

　　The recent American study led by Professor Warren Booth from the University of Tulsa in Oklahoma is the first to document the _(8)_ of virgin births in snakes in the wild. For the scientific world, the results of the research shed new light on the evolutionary and _(9)_ processes of vertebrates. Ultimately, Professor Booth feels that virgin births should no longer be _(10)_ as an evolutionary novelty outside the mainstream of evolution. In other words, they should be seen as having a much bigger influence on the lives of certain animals.

(A) stunned     (B) occurrence      (C) previously (D) of   (E) physically

(F) common    (G) out (H) reproductive    (I) concluded (J) viewed

蛇类处女产子震惊科学家

在自然界中无性生殖愈来愈常见。

美国的研究人员针对野生蛇类已有了令人震惊的发现。至少有些母蛇能够在没有公蛇协助受孕下生育。研究人员在铜头蛇及棉口蛇这两种颊窝毒蛇所出没的自然环境中捕获数十条怀孕的母蛇，并惊讶地发现两例处女产子的个案。科学家们了解繁殖过程中并无公蛇参与。这是因为这两条幼蛇所有的遗传物质均来自母蛇。依据此项研究，研究人员得出结论，百分之二点五到百分之五的幼蛇可能都是这种无性生殖的结果，这种现象又称为单性生殖。

虽然处女产子在诸如蚂蚁和蜜蜂等某些无脊椎动物中相当常见，但在像蛇类等脊椎动物中却是很罕见的。之前曾有被圈养的脊椎动物透过无性生殖而产子的个案。这些罕见的生产案例包括蛇、鲨鱼、蜥蜴，甚至某些品种的鸟类。然而，在所有的案例中，无性生殖只发生在那些被迫迁离自然栖息地以及和雄性动物分居两地的生物身上。

最近这项由美国俄克拉何马州塔尔萨大学的华伦‧布兹教授所带领的研究首次记录了野生蛇类处女产子的事件。对于科学界来说，该研究的结果让人们对脊椎动物的进化与繁衍过程有了新的认识。最后，布兹教授认为处女产子在进化上不应该再被视为主流之外的新鲜事。换句话说，这种现象应被视为是在某些动物的生命中有更大影响力的。

答案： 1.   D   2.   A   3.   G   4.   I     5.   F

      6.   C   7.   E   8.   B   9.   H   10. J