劍橋雅思14Test4Passage1閱讀原文翻譯the secret of staying young

第1段

Pheidole dentata,a native ant of the south-eastern U.S.,isn’t immortal.But scientists have found that it doesn’t seem to show any signs of aging.Old worker ants can do everything just as well as the youngsters,and their brains appear just as sharp.‘We get a picture that these ants really don’t decline,’says Ysabel Giraldo,who studied the ants for her doctoral thesis at Boston University.

Pheidole dentata是美國東南部的一種本地螞蟻，并非永生不死。但科學家發(fā)現它似乎不會展現出任何衰老的跡象。年邁的工蟻可以跟年幼的工蟻一樣很好的完成所有的事情，而且它們的頭腦也同樣敏銳?！拔覀兞私獾剑@些螞蟻真的不會衰老”，Ysabel Giraldo說。她在波士頓大學所做的博士論文就是關于螞蟻的。

第2段

Such age-defying feats are rare in the animal kingdom.Naked mole rats can live for almost 30 years and stay fit for nearly their entire lives.They can still reproduce even when old,and they never get cancer.But the vast majority of animals deteriorate with age just like people do.Like the naked mole rat,ants are social creatures that usually live in highly organised colonies.‘It’s this social complexity that makes P.dentata useful for studying aging in people,’says Giraldo,now at the California Institute of Technology.Humans are also highly social,a trait that has been connected to healthier aging.By contrast,most animal studies of aging use mice,worms or fruit flies,which all lead much more isolated lives.

這種抗衰老的能力在動物王國十分稀有。裸鼢鼠可以活將近30年的時間，并在一生中保持健康。他們甚至在年邁的時候依然可以繁殖，并且從來都不會得癌癥。但是，絕大多數動物跟人類一樣，會隨著年齡增長而衰退。與裸鼢鼠類似，螞蟻是社會型動物，通常生活在具有高度組織的種群中。“正是這種社會復雜性使得Pheidole dentata對研究人類老化十分有用”，加州理工學院的Giraldo說。人類同樣是高度社會化的。這一特點與健康的老去緊密相關。相比之下，大多數研究老化的動物實驗使用老鼠、蠕蟲或者果蠅。所有這些動物的生活都更加孤立。

第3段

In the lab,P.dentata worker ants typically live for around 140 days.Giraldo focused on ants at four age ranges:20 to 22 days,45 to 47 days,95 to 97 days and 120 to 122 days.Unlike all previous studies,which only estimated how old the ants were,her work tracked the ants from the time the pupae became adults,so she knew their exact ages.Then she put them through a range of tests.

實驗室中，P.dentata的工蟻一般可以存活140天左右。Giraldo將注意力放在四個年齡段的螞蟻身上：20到22天，45到47天，95到97天，以及120-122天。與之前那些只評估螞蟻年齡的研究不同，她從蛹變成成蟲時就開始追蹤這些螞蟻，因此她知道他們的準確年齡。然后，她對他們進行了一系列的測試。

第4段

Giraldo watched how well the ants took care of the young of the colony,recording how often each ant attended to,carried and fed them.She compared how well 20-day-old and 95-day-old ants followed the telltale scent that the insects usually leave to mark a trail to food.She tested how ants responded to light and also measured how active they were by counting how often ants in a small dish walked across a line.And she experimented with how ants react to live prey:a tethered fruit fly.Giraldo expected the older ants to perform poorly in all these tasks.But the elderly insects were all good caretakers and trail-followers—the 95-day-old ants could track the scent even longer than their younger counterparts.They all responded to light well,and the older ants were more active.And when it came to reacting to prey,the older ants attacked the poor fruit fly just as aggressively as the young ones did,flaring their mandibles or pulling at the fly’s legs.

Giraldo觀察螞蟻照顧種群中年幼個體的好壞，記錄每只螞蟻照顧、轉移和喂養(yǎng)它們的頻率。她比較了20天大的螞蟻和95天大的螞蟻追蹤氣味的能力。昆蟲一般使用這種氣味來標記通往食物的路徑。她測試了螞蟻對光線的反應，并通過記錄螞蟻在小碟子中穿過某條線的頻率來衡量他們的活躍程度。她還測試了螞蟻對活著的獵物的反應：一只被拴著的果蠅。Giraldo預計年老的螞蟻在所有這些任務中都會表現的更差。但年齡更大的昆蟲在照顧幼蟲和痕跡追蹤方面做的都很好–95天的螞蟻甚至能夠比較為年幼的螞蟻追蹤更遠距離的氣味。它們對光線的反應都十分良好，并且年老的螞蟻更加活躍。至于對獵物的反應，年老的螞蟻在襲擊可憐的果蠅方面跟年幼的螞蟻一樣富有侵略性，張開下頜骨或者撕扯果蠅的腿部。

第5段

Then Giraldo compared the brains of 20-day-old and 95-day-old ants,identifying any cells that were close to death.She saw no major differences with age,nor was there any difference in the location of the dying cells,showing that age didn’t seem to affect specific brain functions.Ants and other insects have structures in their brains called mushroom bodies,which are important for processing information,learning and memory.She also wanted to see if aging affects the density of synaptic complexes within these structures—regions where neurons come together.Again,the answer was no.What was more,the old ants didn’t experience any drop in the levels of either serotonin or dopamine—brain chemicals whose decline often coincides with aging.In humans,for example,a decrease in serotonin has been linked to Alzheimer’s disease.

隨后，Giraldo比較了20天螞蟻和95天螞蟻的大腦，尋找任何接近死亡的細胞。她沒有發(fā)現與年齡相關的巨大差異，正在死去的細胞的位置也沒有什么區(qū)別。這說明年齡似乎沒有影響具體的大腦功能。螞蟻和其他昆蟲的大腦中有被稱為蕈形體的結構。該結構對于處理信息，學習和記憶都很重要。她同樣希望知道老化是否影響這些結構中突觸復合體的密度，即神經聚集的區(qū)域。答案同樣是否定的。此外，老年螞蟻在五羥色胺或多巴胺的水平上也沒有任何下降。這兩種大腦化學物質的下降通常伴隨著衰老。例如，人類中，五羥色胺的下降與阿茲海默癥有關。

第6段

‘This is the first time anyone has looked at both behavioral and neural changes in these ants so thoroughly,’says Giraldo,who recently published the findings in the Proceedings of the Royal Society B.Scientists have looked at some similar aspects in bees,but the results of recent bee studies were mixed—some studies showed age-related declines,which biologists call senescence,and others didn’t.‘For now,the study raises more questions than it answers,’Giraldo says,‘including how P.dentata stays in such good shape.’

“這是首次有人如此徹底地觀察這些螞蟻行為和神經上的變化”，Giraldo說。她最近在Proceedings of the Royal Society B上發(fā)表了自己的發(fā)現?？茖W家也研究了蜜蜂中一些類似的方面，但最近蜜蜂研究的結果十分混雜：一些研究顯示出與年齡相關的衰退，生物學家將其稱之為senescence，而其他則沒有?！澳壳皝碚f，該研究所提出的問題比它解答的更多”，Giraldo說，“這其中就包括P.dentata如何保持這樣良好的狀態(tài)”。

第7段

Also,if the ants don’t deteriorate with age,why do they die at all?Out in the wild,the ants probably don’t live for a full 140 days thanks to predators,disease and just being in an environment that’s much harsher than the comforts of the lab.‘The lucky ants that do live into old age may suffer a steep decline just before dying,’Giraldo says,but she can’t say for sure because her study wasn’t designed to follow an ant’s final moments.

與此同時，如果螞蟻不會隨著年齡而衰退，那么它們?yōu)槭裁催€會死去？在自然界中，由于捕食者、疾病、以及與實驗室舒適條件相比要惡劣的多的環(huán)境，螞蟻可能活不到140天?！斑@些確實活到老年時期的幸運螞蟻可能會在死前經歷急劇的衰退”，Giraldo說。但她并不能肯定，因為她的研究設計并沒有追蹤一只螞蟻的臨終時刻。

第8段

‘It will be important to extend these findings to other species of social insects,’says Gene E.Robinson,an entomologist at the University of Illinois at Urbana-Champaign.This ant might be unique,or it might represent a broader pattern among other social bugs with possible clues to the science of aging in larger animals.Either way,it seems that for these ants,age really doesn’t matter.

“將這些發(fā)現擴展到其他社會性昆蟲十分重要”，伊利諾伊大學厄巴納香檳分校的昆蟲學家Gene E.Robinson說。這種螞蟻可能是獨一無二的。它也可能代表著其他社會性昆蟲中一種更為廣泛的模式，為大型動物中的老化研究提供可能存在的線索。無論如何，對于這些螞蟻來說，年齡似乎真的無關緊要。

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