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已灭绝的平塔岛象龟能否死而复生?

更新时间:2016-1-3 9:09:46 来源:纽约时报中文网 作者:佚名

Scientists Hope to Bring a Galápagos Tortoise Species Back to Life
已灭绝的平塔岛象龟能否死而复生?

The dodo is dead. The passenger pigeon has passed on. But Lonesome George, the iconic Galápagos tortoise whose death marked the end of his species, is in post-mortem luck.

渡渡鸟不存在了,候鸽已经绝迹。人们所知的最后一只加拉帕戈斯象龟亚种——平塔岛象龟“孤独乔治”的去世也标志着该物种的灭绝。幸运的是,平塔岛象龟尚存一丝希望。

A scientific expedition has discovered some of his close blood relations alive and well. With careful breeding, biologists now hope to revive George’s species and reintroduce the tortoises to the island on which they evolved.

科学考察发现,与“孤独乔治”有血缘关系的近亲仍然健康地活着。通过细心的人工哺育,生物学家希望能够复原该物种,并把平塔岛象龟放归到其祖先生活过的岛屿。

It would be a signal achievement in a place that gave rise to our understanding of evolution and speciation.

这将是一次重大成就,能够加深我们对物种进化和形成的理解。

Originally there were at least eight species of Galápagos tortoise, scientists now believe. (One was discovered only this year.) At least three species are now extinct, including tortoises on Pinta Island. The last one, George, was discovered wandering alone in 1972 and taken into loving custody. His death, in 2012 at more than 100 years old, was a powerful reminder of the havoc visited by humans on delicate ecosystems worldwide over the last two centuries.

科学家相信,加拉帕戈斯象龟最初至少有八个不同亚种(今年仅发现了其中一种)。其中至少三种已经灭绝,包括平塔岛象龟。1972年,人类发现了正在孤独流浪的最后一只平塔岛象龟“乔治”,并对它细心照料,直至它以超过百岁的年龄于2012年去世。它的死亡对人类在过去两个世纪对全球脆弱生态系统的破坏是一次巨大的警醒。

Tortoise numbers plummeted from more than 250,000 in the 16th century to a low of around 3,000 in the 1970s. In the 19th century, whalers, pirates and other seafarers plucked the animals from their native islands for use as ballast and food on long journeys. Tortoises can live in a ship’s hold for more than a year without food or water, making them the perfect takeaway meals.

象龟数量从十六世纪的超过25万只急剧下降到二十世纪70年代的约3千只。十九世纪,捕鲸者、海盗和其他航海家将象龟从栖息岛屿掠走,作为长途航行的压舱物和食物。象龟可以在船舱里不吃不喝生存超过一年,使它们成为最佳的“外卖”食物。

There are two types of Galápagos tortoises: saddlebacked and domed. The sailors much preferred the smaller saddlebacks, which were easier to lug around and said to taste better. They were also easier to find: Domed tortoises live at higher elevations and can weigh 300 pounds. Saddlebacks evolved at lower elevations and feed on drier vegetation.

加拉帕戈斯象龟有两种——鞍背龟和穹背龟。由于携带更方便,且据说更美味,海员更偏爱体型较小的鞍背龟。并且,鞍背龟也更容易被发现,因为穹背龟生活在高海拔地区,重量可达300磅,而鞍背龟在低海拔地区繁衍,以干燥植物为食。

Saddlebacked tortoises disappeared from Santa Fe Island and Floreana Island, a favorite hangout for sailors posting letters for other ships to carry home. With George’s death, the Pintas were gone, too.

鞍背龟相继从圣菲岛和弗罗里安那岛消失,海员热衷于从这两处岛屿让其他过往船只将自己的书信带回家。随着“乔治”的死亡,平塔岛上的鞍背龟也绝迹了。

But now the story of extinct Galápagos tortoises has taken a strange, and hopeful, twist.

不过现在,已经灭绝了的加拉帕戈斯象龟迎来了一次奇妙却充满希望的转机。

More than a century ago, it turns out, sailors dumped saddlebacked tortoises they did not need into Banks Bay, near Wolf Volcano on Isabela Island. Luckily, tortoises can extend their necks above water and float on their backs. Many of them made it to shore, lumbered across the lava fields and interbred with Isabela’s native domed tortoises.

一百多年前,一些海员将他们不再需要的鞍背龟丢弃在了伊莎贝拉岛沃尔夫火山附近的班克斯湾。幸运的是,这些象龟可以将长长的脖子伸出水面,并且仰面漂浮。许多象龟就这样漂到了岸边,缓慢地爬过溶岩区,与伊莎贝拉岛上栖息的穹背龟交配繁衍。

In 2008, scientists tagged and collected blood samples from more than 1,600 tortoises living on the flanks of the volcano. Back in the laboratory, there was a genetic eureka: Eighty-nine of the animals were part Floreana, whose full genetic profile DNA had been obtained from museum samples.

2008年,科学家为生活在火山两侧的1600多只象龟作了标记并提取血液样本。把样本带回实验室后,科学家在遗传学方面有了重大发现:其中89只象龟来自弗罗里安那岛,科学家已经从博物馆样本上获得了它们的完整DNA基因图谱。

Some had genes indicating their parents were living purebred Floreana tortoises, hinting that the species may not be extinct after all.

一些样本携带的基因显示它们的父辈是现存的纯种弗罗里安那象龟,表明这一物种或许根本没有灭绝。

Seventeen tortoises were shown to have high levels of Pinta DNA. Tortoises can live for more than 150 years, so some of them may well be George’s immediate next of kin.

17只象龟的样本携带较多的平塔岛象龟DNA。象龟寿命超过150年,因此其中一些象龟或许是“乔治”的直系近亲。

Last month, scientists went back to find them. Their plan was to capture and separate tortoises with high levels of Pinta and Floreana DNA, and then breed animals that are genetically closest to the original species.

科学家上个月前往沃尔夫火山寻找象龟。他们计划捕捉几只象龟,根据其携带的平塔岛象龟和弗罗里安那象龟DNA数量进行区分,并对遗传学上最接近原始物种的象龟进行人工哺育。

In just a few generations, it should be possible to obtain tortoises with 95 percent of their “lost” ancestral genes, the scientists said.

科学家认为,经过几代繁殖,人们可能会得到携带95%已消失的祖先基因的象龟。

“The size of this population is mind-boggling,” said Adalgisa Caccone, a senior research scientist at Yale University and the expedition’s geneticist, said of the Wolf tortoises. “I am optimistic that some of these animals will have high conservation value.”

耶鲁大学高级研究员、科考队遗传学家阿达吉萨.卡康(Adalgisa Caccone)在谈到沃尔夫象龟时表示:“数量之大令人难以置信。”“其中一些象龟将拥有较高的物种保护价值,对此我非常乐观。”

Genetics is increasingly a key component of conservation management worldwide, said Dr. Linda Cayot, science adviser for the Galápagos Conservancy, which helped sponsor the expedition with the Galápagos National Park Service.

与加拉帕戈斯国家公园共同发起此次科学考察的加拉帕戈斯象龟保护机构科学顾问林达.卡洛特(Linda Cayot)博士表示,遗传学正在逐渐成为全球物种管理的重要组成部分。

But “this is the first time that genetic information has been used so determinedly,” she said, to manage a species and its environment.

但“这是科学家首次如此坚定地运用遗传信息”管理某个物种及其生存环境,她说。

With captive breeding and luck, new populations of tortoises could be released on Pinta and Floreana Islands in five to 10 years, helping to restore their lost ecosystems, Dr. Cayot said. Because tortoises cruise close to the ground, they disperse seeds and other nutrients that keep the land healthy.

卡洛特博士认为,经过悉心哺育,再加上一些运气,新象龟群体有望在五至十年后放还到平塔岛和弗罗里安那岛,帮助重建那里已经消失的生态系统。由于龟龟常在地表活动,它们可以散播种子和其他营养物,以保持土壤健康。

The expedition to Wolf Volcano occurred over the last 10 days of November under the direction of James P. Gibbs, a professor of vertebrate conservation at the State University of New York in Syracuse. Nine three-person teams were deployed over a 20-square-mile area.

在锡拉丘兹市纽约州立大学脊椎动物保护专业教授詹姆斯.吉布斯(James P. Gibbs)的带领下,沃尔夫火山科考已经在11月下旬展开。九个3人小组在超过20平方英里的区域工作。

It was rough going, with razor-sharp lava underfoot, and ticks and wasps all around.

脚下锋利的火山岩和遍布各处的蜱虫和黄蜂使工作困难重重,进展缓慢。

The teams were looking for tortoises with the most prominent saddlebacks: shells rising up in front, like saddles, to accommodate the animals’ extremely long necks for grazing on tall cactuses. The hope is that animals with characteristic shells will have the highest levels of Pinta and Floreana DNA.

科考队正在寻找最典型的鞍背龟:龟壳前部像马鞍一样隆起,确保象龟伸出长长的脖子,吃到高大的仙人掌。研究认为,具有此类特征龟壳的象龟会携带最多的平塔岛和弗罗里安那岛象龟的DNA。

Two teams found “hot spots” of saddlebacks at the southern end of the search area with low-lying, dry vegetation, Dr. Gibbs said. The best specimens were captured relatively close to one another.

吉布斯博士说,两个小组在低洼且有干燥植物的搜寻区南端发现了鞍背龟的主要活动区域。他们在颇为接近的地方捕获了几只象龟作为最佳样本。

The pattern is remarkable, Dr. Gibbs said. After being jettisoned into Banks Bay more than a century ago, the saddlebacks have not moved more than a few miles. They found food and water, so why bother?

这是一种最佳方式,吉布斯博士认为。一百多年前被遗弃在班克斯湾后,鞍背龟的活动区域仅移动了不超过几英里。它们在那里找到了食物和水,何乐而不为呢?

In all, the expedition discovered more than 100 giant tortoises that share George’s distinctive saddleback shape. When a team captured a tortoise with an ideal saddleback, they called the expedition’s ship, anchored in Banks Bay. A helicopter then fetched the animal in a cargo net.

最终,科考队发现了100多只与“乔治”一样拥有独特马鞍形状的巨型象龟。其中一个小组在捕获一只典型鞍背龟时,他们让科考船驶进班克斯湾,用直升机将巨龟罩在装卸网中吊起。

Scientists took 32 tortoises with the most spectacular saddles to a breeding center on Santa Cruz Island. The captured tortoises include 21 females and 11 males, each weighing 100 to 300 pounds. Most appear to be 30 to 40 years old, Dr. Gibbs said, though a few could be much, much older.

科学家将32只拥有最典型马鞍状龟壳的象龟带回圣克鲁斯岛的繁育中心。其中包括21只雌龟和11只雄龟,重量为100至300磅。吉布斯博士表示,大多数的龟龄在30至40岁,也有一些要年长很多。

Seven of the animals tagged and analyzed in 2008 were retrieved — one male and one female with Pinta DNA, and one male and four females with Floreana genes. “We are planning to go back next year to look for more,” Dr. Gibbs said.

七只象龟在2008年经过标记和分析后被放归,其中一只雄性和一只雌性携带平塔岛象龟DNA,另外一只雄性和四只雌性携带弗罗里安那岛象龟的基因。“我们正计划明年重返那里寻找更多象龟。”吉布斯博士说。

Today, the female tortoises are housed in Lonesome George’s corral. The males are next door in a tourist pen.

如今,其他雌龟圈养在“孤独乔治”曾经用过的围栏内,雄龟则在隔壁供游客观赏。

“They are very busy, very happy, exploring and doing aggression displays,” Dr. Caccone said. “Males stand on three legs, necks raised as high as they can go, and hiss at each other.”

“它们很忙,很快乐,不断探索着周围的环境,时常摆出一幅不可一世的样子。”卡洛特博士说。“雄龟常会三条腿站立,尽可能伸长脖子,彼此发出嘶嘶声。”

The next step is to analyze each animal’s DNA to separate the two species and find those with the least mixed ancestry. Then the breeding program can begin.

下一步是要分析每只龟的DNA,以区分两个不同物种,寻找血统最纯正的象龟。人工哺育计划就可以随即开始。

“If I had the money and people, it would take me a month” to do the analysis, said Dr. Caccone, noting the expedition’s tight budget. Realistically, she said, it may take a year or more.

卡洛特博士表示,“如果能确保资金和人力,将需要一个月”进行分析,这表明科考项目预算紧张。因此乐观估计,分析工作将持续一年或更久。

One of the males is a doppelganger for Lonesome George, said Elizabeth Hunter, a postdoctoral researcher on the expedition from the University of Georgia. When first captured, he raised himself up in a classic George pose.

科考队内来自乔治亚大学的博士后研究员伊丽莎白.亨特(Elizabeth Hunter)认为,其中一只雄龟与“孤独乔治”面貌极其相似。在首次被捕获时,它以典型“乔治”的姿势昂起身。

He is now showing off for tourists, just like the old George.

它现在与“乔治”生前一样,向游客炫耀着自己的雄风。

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