剑桥雅思14Test4Passage1阅读原文翻译 the secret of staying young 年轻的秘密
剑桥雅思14 Test4 Passage1阅读原文翻译
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是美国东南部的一种本地蚂蚁，并非永生不死。但科学家发现它似乎不会展现出任何衰老的迹象。年迈的工蚁可以跟年幼的工蚁一样很好的完成所有的事情，而且它们的头脑也同样敏锐。“我们了解到，这些蚂蚁真的不会衰老”，Ysabel Giraldo说。她在波士顿大学所做的博士论文就是关于蚂蚁的。
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.
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.
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观察蚂蚁照顾种群中年幼个体的好坏，记录每只蚂蚁照顾、转移和喂养它们的频率。她比较了20天大的蚂蚁和95天大的蚂蚁追踪气味的能力。昆虫一般使用这种气味来标记通往食物的路径。她测试了蚂蚁对光线的反应，并通过记录蚂蚁在小碟子中穿过某条线的频率来衡量他们的活跃程度。她还测试了蚂蚁对活着的猎物的反应：一只被拴着的果蝇。Giraldo预计年老的蚂蚁在所有这些任务中都会表现的更差。但年龄更大的昆虫在照顾幼虫和痕迹追踪方面做的都很好 – 95天的蚂蚁甚至能够比较为年幼的蚂蚁追踪更远距离的气味。它们对光线的反应都十分良好，并且年老的蚂蚁更加活跃。至于对猎物的反应，年老的蚂蚁在袭击可怜的果蝇方面跟年幼的蚂蚁一样富有侵略性，张开下颌骨或者撕扯果蝇的腿部。
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.
‘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.’
“这是首次有人如此彻底地观察这些蚂蚁行为和神经上的变化”，Giraldo说。她最近在Proceedings of the Royal Society B上发表了自己的发现。科学家也研究了蜜蜂中一些类似的方面，但最近蜜蜂研究的结果十分混杂：一些研究显示出与年龄相关的衰退，生物学家将其称之为senescence，而其他则没有。“目前来说，该研究所提出的问题比它解答的更多”，Giraldo说，“这其中就包括P. dentata如何保持这样良好的状态”。
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.
‘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.
“将这些发现扩展到其他社会性昆虫十分重要”，伊利诺伊大学厄巴纳香槟分校的昆虫学家Gene E. Robinson说。这种蚂蚁可能是独一无二的。它也可能代表着其他社会性昆虫中一种更为广泛的模式，为大型动物中的老化研究提供可能存在的线索。无论如何，对于这些蚂蚁来说，年龄似乎真的无关紧要。