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Science and technology
科學技術
Marine biology
海洋生物學
Scents and sensibility
氣味與識別
Turtles love a smell that humans loathe. For them, it means dinner
海龜喜歡一種人類討厭的味道，對它們來說，這表示大餐
JELLYFISH may not be most people's idea of a tasty snack, but if you are a loggerhead turtle, they are top of the menu.
水母或許不符合大多數人對于美味小食的定義，但如果你變成一只紅海龜，水母便成了頂級美食。
Though jellyfish can swim, they are not exactly the greyhounds of the ocean, so they are easily caught.
雖然水母可以游動，但它們可算不上海洋中的快艇，所以要逮它們很容易。
And since munching a large jellyfish can keep a turtle going for days, loggerheads love them when they can find them.
而吃上一只大水母能讓一只海龜維持好幾天，所以紅海龜一旦發現水母便會大快朵頤。
Yum！
味道好極了！
The best place to do so is in an upwelling zone.
上升流區是海龜大快朵頤的最佳地點。
This is an area where the wind's action draws cold, nutrient-rich water to the surface.
在這種區域里，水流會在海風的作用下將富含營養物質的冷水帶到海洋表面，
That encourages the growth of planktonic algae, and thus of everything that feeds on such plankton, or feeds on what feeds on them—including jellyfish, and also various molluscs and crustacea that loggerheads enjoy as an appetiser.
這有利于浮游藻類生長，因此也有利于以這些浮游生物為食的動物，或以這些動物為食的動物生長，包括水母，還有各種各樣的軟體動物和甲殼動物，這些都是紅海龜的最愛。
And upwelling zones do, indeed, attract turtles.
所以上升流區確實會吸引海龜，
But nobody knows how, for such zones are scattered, local and often temporary phenomena, and locating them in the wide expanse of the sea is hard.
但沒人知道海龜是怎樣找到上升流區的，這些區域都是局部性的，非常分散，且常常只是暫時現象，要想在寬廣的海洋中找到它們絕非易事。
Courtney Endres, a biologist at the University of North Carolina at Chapel Hill, however, thought the reptiles might be smelling such zones from afar.
然而考特尼恩德斯認為兩棲動物離很遠便能通過氣味察覺到上升流區，她是美國北卡羅來納州立大學的一名生物學家。
She knew from an experiment she conducted a few years ago that loggerheads have a good sense of smell.
她是從幾年前進行的試驗中發現紅海龜擁有良好的嗅覺。
She also knew, because passing sailors frequently comment on the fact, that upwelling zones tend to stink.
她還了解到上升流區往往會發出異味，因為經過上升流區的水手們經常會提到這一事實。
Specifically, they stink of cabbages.
明確的說，是卷心菜的異味。
That is because many planktonic algae, when crunched up during the process of being eaten, release a substance called dimethylsulphoniopropionate.
這是由于浮游藻類在被吃掉的過程中被咬碎時，會釋放出一種叫做硫代甜菜堿的物質，
This quickly degrades into another chemical, dimethyl sulphide, which generations of those subjected to unimaginative school lunches will instantly recognise.
該物質很快會降解為另一種化學物質-二甲基硫化物，聞到這種物質產生的氣味會立刻讓人想起千篇一律的學校午餐的氣味。
But to loggerheads it is the smell of a banquet.
但這對紅海龜來說是盛宴的氣息。
Ms Endres and her colleague Kenneth Lohmann showed this by collecting 11 loggerhead hatchlings from local beaches and testing them to see which smells most interested them.
恩德斯及其同事肯尼斯羅曼通過實驗表明了這點。她們在當地海灘上抓了11只紅海龜的幼龜，并測試它們對哪種氣味最感興趣。
The young turtles were each put in a tank of seawater that had various scents blown across its surface.
每只幼龜被分別放入一個裝有海水的水缸中，并將各種各樣的氣味吹過水面，
These included cinnamon, jasmine, lemon—and dimethyl sulphide.
包括肉桂，茉莉，檸檬，以及二甲基硫化物。
When a turtle came up for air , the researchers recorded how long it sniffed around.
當海龜到水面上換氣時，研究人員記錄了它們露出水面的時間。
They found, as they report in Experimental Biology, that the animals spent an average of five seconds breathing air scented with lemon,jasmine or cinnamon, all pleasant odours from a human point of view.
他們發現，從人類的角度上看，檸檬，茉莉，或肉桂都是很悅人的氣味，而海龜在呼吸含有以上氣味的空氣時，平均只在水面停留了五秒鐘，
That was no different from the amount of time they spent at the surface when no scent was used at all.
與在其呼吸沒有氣味的空氣時的停留時間沒什么不同。
When the air was scented with dimethyl sulphide, however, they spent an average of ten seconds breathing in the stinky scent of cabbages—or upwellings.
然而在空氣中含有二甲基硫的氣味時，海龜在這種散發著卷心菜或者說上升流異味的空氣中平均停留了十秒鐘。該報道刊登在《實驗生物學》上。
That does not prove that loggerheads smell their way to the table, of course. But it makes the hypothesis plausible.
當然，這并不能證明紅海龜能順著氣味找到它們的餐桌，但是這讓以上假設似乎可以說得通。
For turtles, it seems, the perfumes of Araby hold little charm.
看來阿拉伯香水對海龜也不會有什么吸引力，
The scent of cabbages, by contrast, is as attractive as the odour of roasting chicken is to a hungry human.
相比之下，卷心菜的氣味之于海龜的吸引力就像烤雞之于餓漢。
