鯊魚知道長壽的秘密

鯊魚知道長壽的秘密

地球上最長壽脊椎動物很可能是鯊魚——最近在格陵蘭島附近的北冰洋域發(fā)現(xiàn)小頭睡鯊，年紀(jì)最大的已有400多歲。

測試中可能遇到的詞匯和知識：

stalk 追蹤，潛近[st??k]

specimen 樣品，樣本；標(biāo)本['spes?m?n]

vertebrate 脊椎動物['v??t?br?t]

succor 救援物品['s?k?]

snare 捕捉；誘惑[sne?]

radiocarbon [核] 放射性碳[,re?d???'kɑ?b(?)n]

sobering 使清醒的['s??b?r??]

intone 吟誦；吟詠[?n't??n]

mishap 災(zāi)禍；不幸事故['m?sh?p]

mammalian 哺乳類動物的[m?'me?l??n]

immortality 不朽；不朽的聲名；不滅[?m??'t?l?t?]

elixir 不老長壽藥；萬能藥；煉金藥[?'l?ks?; -s??]

abstinence 節(jié)制；節(jié)欲；戒酒；禁食['?bst?n?ns]

eternal 永恒的；不朽的[?'t??n(?)l; i?-]

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Sharks hold secret to a longer life（615words）

By Anjana Ahuja

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There are Methuselahs among us. These aged wonders of the natural world do not stalk the earth but glide through Arctic waters. Scientists surveying Greenland sharks, previously thought to live up to 200 years, found that they have far longer lifespans. One specimen was calculated, give or take a century, to be nearly 400 years old, born more than a century before the US was founded.

The discovery, reported last week in the journal Science, is a record for a vertebrate, and potentially gives succour to those searching for the secrets of longevity. Anti-ageing enthusiasts insist that life is merely the absence of the processes that lead to death, and that human lifespan could be extended dramatically. Their philosophy is to treat ageing as a disease: treat the disease and life need not end.

Sharks and rays usually reveal their ages through the calcium deposits laid down each year in hard structures such as fins, but Greenland sharks, the largest fish in northern waters, have no such structures. Instead, researchers, presented with 28 females snared accidentally in fishing nets, looked to sharks’ eye lenses. Tissues formed in the lens at birth remain unchanged; its radiocarbon (a radioactive isotope of carbon) content can be matched to the known levels of radiocarbon in the marine environment stretching back 500 years. In effect, a shark’s eye lens contains a radiocarbon time-stamp of its birth.

An international team, led by academics at the University of Copenhagen, showed that the largest sharks — one stretched to 5m — were generally the oldest, with one dated at about 392 years old. The females are estimated to reach sexual maturity at 156. Their eyes also provide a sobering window on human history: the lenses of the youngest fishes contained a “bomb pulse”, a distinctive radiocarbon signature resulting from nuclear weapons testing.

The study intones, rightly, that we should guard these centenarians of the deep; their leisurely pace of maturity and reproduction has obvious consequences for conservation. But it also shows there are potentially many longer-lived species than humans, raising questions anew about whether there really is any natural bar to humans living for centuries. After all, life expectancy has been rising for decades as we conquer the challenges — malnutrition, disease, war, mishap — that hasten our passing. Three centuries ago, a person would be hard pushed to reach 40; some scientists think those born today stand a fighting chance of reaching 150.

Currently, the Japanese are the flag-bearers, boasting a life expectancy of 83 (life expectancy is the average age reached by a population; lifespan is the number of years lived by a particular individual). The longest verified lifespan is 122 years. Humans are not going to outlive sharks any time soon, but new records are being set in mammalian species. This year, scientists found that mice could be engineered to live 35 per cent longer simply by clearing ageing cells from the body. Such laboratory breakthroughs have transformed the quest for immortality from laughing stock to biotech stock. The mission statement of Calico, an Alphabet-backed life sciences start-up, has been paraphrased as “curing death”. Human Longevity, a company focusing on genome research into ageing, boasts a stellar line-up of backers. Meanwhile, hedge fund manager Joon Yun has set up the $1m Palo Alto Longevity prize to “hack the code” for ageing.

In the absence of an elixir, there is some evidence, albeit mixed, that cutting calories may extend life in mice and monkeys. Members of the Calorie Restriction Society advocate partial abstinence as the route to long life. I suspect, however, that forgoing chips and chocolate cake simply makes life feel longer than it really is, and is instead the secret of eternal boredom.

請根據(jù)你所讀到的文章內(nèi)容，完成以下自測題目：

1. Which kind of sharks can live about 400 years?

A. goblin sharks

B. hammerhead sharks

C. greenland sharks

D. thresher sharks

2. What do scientists find in shark’s eye lens to know sharks’ lifespan?

A. sodium

B. radiocarbon

C. iodine

D. potassium

3. When are the female sharks estimated to reach sexual maturity?

A. 99

B. 176

C. 156

D. 210

4. Which one is not the reason that hasten human’s passing?

A. malnutrition

B. haleness

C. disease

D. mishap

[1] 答案 C. greenland sharks

解釋：格陵蘭鯊魚是海洋界壽命最長的鯊魚，能活到400歲。

[2] 答案 B. radiocarbon

解釋：科學(xué)家研究發(fā)現(xiàn)在此種鯊魚的眼睛里有著一種特殊的物質(zhì)---放射性碳，可以估算出鯊魚的年齡。

[3] 答案 C. 156

解釋：雌性鯊魚要到156歲才能進(jìn)入性成熟期。

[4] 答案 B. haleness

解釋：營養(yǎng)不良，疾病災(zāi)禍都會導(dǎo)致人類生命的加速終結(jié)。