Why were scientists so obsessed with these frogs? - Carly Anne York

翻译人员: Jacky He 校对人员: Yip Yan Yeung

From the 1930s well into the 1960s,

自 1930 年代一直到 1960 年代，

pregnancy testing required a slippery piece of equipment:

孕检需要一种滑溜溜的工具：

a female African clawed frog.

雌性非洲爪蛙 (African clawed frog) 。

For decades, hospitals and research labs around the world

数十年来，在世界各地的医院与研究所

had a trusted supply of these handy amphibians,

这些两栖动物的供应不断，

employing their help in testing for pregnancy

用来检测怀孕，

and in numerous other scientific endeavors.

或是其他科学实验。

So, what makes these phenomenal frogs so special?

那么，是什么让这些 特别的青蛙如此突出？

The remarkable features of the African clawed frog

非洲爪蛙的独特之处

have fascinated researchers since the 19th century.

从 19 世纪以来 一直使研究者着迷。

We often think of frogs as hopping around to snatch up bugs

我们通常认为青蛙 跳来跳去，用它们的

with their lengthy tongues.

长舌捕获虫子。

But this water-dwelling species is almost exclusively aquatic,

但这个水栖物种几乎完全水生，

having adapted primarily for swimming rather than crawling or jumping.

进化出游泳， 而非爬行、跳跃的本事。

Weirder still, African clawed frogs have no tongues at all.

更奇怪的是， 非洲爪蛙根本没有舌头。

Instead, they suck food directly into their mouths

它们将食物直接吸入嘴中，

or use their hands to catch larger animals

或是用前肢捕获大型猎物，

which they tear apart with powerful hind claws.

并用强力的后爪撕碎。

To help get close to their prey,

为了接近猎物，

their smooth skin can quickly change color to blend into their surroundings.

它们的光滑皮肤可以迅速 改变颜色，融入周围环境。

This camouflage ability was particularly interesting to a trio of biologists

这项伪装能力尤其被 1920 年代

in South Africa during the 1920s.

三位南非生物学家所关注；

Hillel Shapiro, Harry Zwarenstein, and their teacher, Lancelot Hogben,

希勒尔·夏皮罗、哈利·兹瓦伦斯坦、 和他们的导师，兰斯洛特·霍格本

were researching what role the pituitary gland,

在探究垂体——

a small region of the frog’s brain,

青蛙大脑中的一小块区域，

might play in the color changing mechanism.

在变色机制中的潜在作用。

Removing the gland altogether impaired the frogs’ ability to camouflage.

移除垂体使青蛙无法伪装。

But when Hogben injected them with a pituitary extract derived from an ox,

但当霍格本给它们注射 公牛的垂体提取物后，

he found an even more surprising result—

他发现了更加反常的现象——

the frogs began laying eggs.

青蛙开始产卵。

Normally, African clawed frogs only release eggs

通常情况下，非洲爪蛙产卵的前提

when a male frog is nearby to fertilize them.

是雄蛙给它们授精。

But this ox hormone triggered their ovulation without the presence of a male.

但公牛的荷尔蒙致其 在没有雄性的情况下排卵。

And this process gave the researchers an idea.

这个原理启发了研究人员。

They knew there was a chemical similarity between the ox hormone

他们知道公牛荷尔蒙与孕妇

and a hormone found in the urine of pregnant people—

尿液中的荷尔蒙存在相同之处——

a compound we know today as the chorionic gonadotropin hormone, or hCG.

我们今天称之为 绒毛膜促性腺激素 (hCG)。

In pregnancy tests of the day,

在以前的孕检中，

animals like mice and rabbits were injected with human urine

大白鼠、兔子等 动物被注射人类尿液，

as a way of testing for the presence of hCG.

以检验 hCG 的存在。

However, this required multiple days of injections,

不过，这需要好几天的注射，

as well as killing and dissecting the animals

还要杀死、解剖动物，

to see whether the hormone was present.

以检验荷尔蒙。

Because of these hurdles, the test was reserved for specific use cases,

因为过程麻烦， 测试只针对具体场景，

leaving most people waiting for visible signs to determine if they were pregnant.

于是大部分人只能 依赖明显的怀孕征兆。

But these frogs changed everything.

但这些青蛙改变了一切。

They responded to hCG in roughly 9 hours with no need for dissection.

它们会在大概 9 小时以内 对 hCG 起反应，不需解剖。

And since their large ovaries constantly generate eggs,

而由于它们的巨大卵巢 不停地产生卵子，

they could participate in numerous tests over their 15 to 30 year lifespan.

它们能在 15 到 30 年的 生命周期中参与多场检验。

Better still, these frogs were abundant in their native habitat,

更佳的是，这些青蛙 在栖息地数量庞大，

making them easy to find, catch, and export.

容易被找到、捕获并出口。

Before long, tens of thousands of African clawed frogs

不久之后，数以万计的非洲爪蛙

were being shipped to hospitals all over the world,

被运送至世界各地的医院，

making reliable pregnancy tests widely available for the first time.

可靠的孕检第一次面向大众。

In the 1970s, the frogs would be superseded by chemical tests

在 1970 年代， 青蛙被直接检测 hCG 的

that detected hCG directly.

化学测试所取代。

But by then their widespread presence in laboratories

但它们在实验室中的广泛使用，

had made African clawed frogs the star of numerous studies.

意味着非洲爪蛙 成为了众多研究的对象。

Their rapid development and ability to produce eggs in any season

它们的快速成熟， 和在任何季节产卵的能力

made them invaluable models for developmental biology.

意味着它们是 生长生物学的珍稀模型。

African clawed frogs have even been part of biological studies

非洲爪蛙甚至还参与了 奋进号航天飞船上的

aboard the Space Shuttle Endeavour.

一系列生物研究。

However, frogs can be slippery subjects.

不过，青蛙也是灵活的实验对象。

More than a few of these amphibians have escaped their laboratory enclosures,

一些逃离了它们的实验室环境，

and in many places,

在很多地方，

their ferocious appetite allowed them to outcompete native amphibians.

它们的大胃口使其 超过了本土两栖动物。

To make matters worse,

更糟糕的是，

they often carry a deadly fungus called chytrid,

它们经常携带名为壶菌 (chytrid) 的致命真菌，

which can cause an infection that lethally disrupts

能导致感染，彻底破坏

the delicate functioning of amphibian skin.

两栖动物敏感的皮肤功能。

In the 20th century, this fungal infection has devastated amphibian populations

在 20 世纪，这类真菌感染 重创了世界各地的

around the globe,

两栖动物种群，

causing the extinction of multiple frog species.

致使多个青蛙物种灭绝。

Because of all these concerns,

出于这些顾虑，

the African clawed frog is now classified as an invasive species,

非洲爪蛙现被归为入侵物种，

and illegal in many regions.

在许多地区是禁止的。

So in the end, like other pregnancy tests,

总而言之，像其他孕检一样，

the use of these frogs in scientific research

科学研究中对于青蛙的运用

has had both positive and negative results.

带来了正负面的影响。