游弋在爱尔兰水域的精灵英语美文
Why Do Insects Stop "Breathing"
为什么昆虫会有规律地停止呼吸?日前，美国及德国的科学家们对这一问题给出了最新的解释。他们认为，昆虫之所以会有如此举动是为了避免吸入对身体有害的过量氧气。
Challenging previous theories, researchers at UC Irvine and Humboldt University propose that insects such as grasshoppers, moths, butterflies, some types of fruit flies, beetles and bugs close off their respiratory systems periodically to keep out excess oxygen, thus preventing damage to their tissues.
为什么昆虫会有规律地停止呼吸?日前，美国及德国的科学家们对这一问题给出了最新的解释。他们认为，昆虫之所以会有如此举动是为了避免吸入对身体有害的过量氧气。
据美国“每日科学网站”2月24日报道，通过对昆虫的呼吸系统进行深入的研究，科学家们或许已经可以揭晓这个在人们心中存在了数十年的谜团。美国加州大学尔湾分校和德国洪堡大学的研究者提出，像蚱蜢、蛾、蝴蝶和果蝇等昆虫会周期性地关闭它们的呼吸系统，以避免吸入过量的氧气，从而使自己的身体组织免受伤害。这一结论则向以前的相关理论发出了挑战。
对于昆虫有规律地屏住呼吸的问题，以前科学家们曾提出了两种解释。
一种理论认为，这种间断地不连续地呼吸可以帮助昆虫减少水分的流失;而第二种理论则认为，当昆虫在地下的时候，这种特别的呼吸方式能使它们从其呼吸作用的副产品——二氧化碳中摆脱出来。因为，当昆虫处在地面下的时候，它们面临的是一个高二氧化碳同时低氧的环境。这时，氧气对昆虫至关重要，但是从高浓度的二氧化碳中解脱出来，避免在身体组织中产生毒性也同样具有重要的意义。
美国加州大学尔湾分校的生态学及进化生物学教授蒂莫西·布拉德利和德国洪堡大学的生理学助理教授斯特凡·黑茨对这一问题进行了深入研究，并提出了一个更为合理的解释。他们认为，许多昆虫关闭气孔、屏住呼吸是为了避免吸入过量的氧气。他们将这一研究结果发表在2月份的国际性科技期刊英国著名的《自然》杂志上。
研究显示，昆虫在飞行等高度活动的状态下，会正常呼吸。 但是当它们处在不活跃状态或是休息的时候，他们仍继续在浓度不变的高氧环境中进行呼吸，其结果就会导致它们吸入过量的氧气，而体内氧气过量则会导致昆虫的身体组织出现氧化损伤。为了使身体免受伤害，一些昆虫(如蚱蜢等)则会选择间歇性停止呼吸这一做法。
对此，布拉德利教授表示：“我们认为大部分昆虫有规律地间歇性呼吸是为了降低
Something Fishy
这种30厘米长，身上带有条纹的cuckoo wrasse鱼在爱尔兰水域很常见。所有的cuckoo wrasse鱼刚生下来时都是雌性的，后来其中的一些雌鱼在当了几年母亲后，会转变成雄鱼。雄鱼会在它的领地里起支配作用，但等它死了之后，就会有一只雌鱼转变为雄鱼来接替它的位置。
In clown stripes and swirls, a foot-long (30-centimeter-long) cuckoo wrasse (Labrus mixtus), common in Irish waters, hovers over a vivid sea floor off Valentia Island. All cuckoos are born female; some become males later in life, usually after experiencing motherhood for several years first. A single male will dominate his habitat. When he dies, a top-ranking female will transform to take his place.
有些生物学家认为这种手指长的红色鳚鱼(red blenny)只生活在葡萄牙海域。但事实证明，这种小鱼的生活范围要比人们想像的宽阔得多。摄影师布莱恩·史盖瑞就在爱尔兰西南海岸附近的岩石裂缝中，捕捉到了这种小鱼的身影。
Some biologists thought that the finger-long red blenny (Parablennius ruber, also called a Portuguese blenny) lived exclusively in Portuguese waters. Turns out the little fish"s home range is quite a bit bigger. Photographer Brian Skerry spied this one peeking from a crevice near Ireland"s southwest coast. "We found they were common off Valentia Island," he says.
在苏格兰和爱尔兰西部沿海，拥有200多只触须的珍稀海葵让人们感受到了这种难得一见的美丽。
Churning up silt some 80 feet (24 meters) down, the rare burrowing fireworks anemone (Pachycerianthus multiplicatus), with up to 200 tentacles, has been recorded in just a handful of spots off the west coast of Scotland and Ireland.
Local marine biologist Nick Pfeiffer led photographer Brian Skerry out to see the soccer-ball-size animals in a protected bay in Connemara. "Knowing how scarce they are," says Skerry," it was like making a new discovery when we came upon them." (：夏根建)
体内的氧气浓度，以保证生理上的安全。它们充分减少气体交换频率，使体内的氧量保持在一个安全的水平。这种假设可以解释不同环境下昆虫的呼吸模式，而以前的理论则无法做到这点。”
在研究过程中，科学家用一只乌桕大蚕蛾的蛹做了试验。昆虫没有肺，所以它们使用通气孔进行呼吸。科学家把导管插入到蛾蛹的通气孔中，以测量它排放的二氧化碳量及吸入的氧气含量。研究者还使用呼吸计(一种测量呼吸作用的仪器respirometer)监测飞蛾的呼吸形态。
布拉德利教授解释说，通常昆虫呼吸系统中的氧气含量会保持在4-5千帕斯卡，比大气中的氧气含量要低4至5倍。
通过改变蛾蛹周围环境的氧含量，研究者发现，在氧气含量正常的环境中，昆虫呼吸一段时间，并释放大量二氧化碳，然后它就会关闭通气孔，以阻挡更多的氧气进入。在氧气含量较低的环境中，昆虫就会将通气孔开放的时间延长，关闭的时间缩短。同时，如果在氧气含量较高的环境中，昆虫只会在很短的时间里打开通气孔，随后就将之关闭很长一段时间。换句话说，就是昆虫能积极地对氧气含量的多少作出反应，通过开关通气孔，昆虫可以使体内的氧气和二氧化碳含量保持在相当稳定的水平。这在某种程度上显示它们能够自行衡量氧气的多少。布拉德利教授说：“它们的行为告诉我们，它们可以对氧气含量进行调节。”
研究这个问题，就不得不提到氧气与生物体的关系问题。众所周知，氧气是生命之源。但是吸入的氧气过量也会导致生物体死亡。身体组织暴露在活性很强的氧分子中，会使蛋白质、脂类和DNA受损，促使细胞死亡、加快衰老。
对此，研究者表示，即使在我们的身体中，这种情况也是存在的。我们的身体也会向各个组织器官提供氧气。同样道理，人们也在尽力避免过量的氧气对身体带来的伤害——氧化损伤。这种损伤和人们衰老过程有着紧密的联系。或许这就是为什么市场上会出现众多的抗氧化护肤品的原因——人们也在想尽一切办法抵抗衰老。空气中，如果我们呼吸的氧气浓度过高，这对人体是具有毒性的。事实上，作为分析对象被科学家们反复研究了数十年的果蝇，如果被置于一个高氧的环境中，就会很快因为衰老而死亡。
报道说，科学家们还将在这一领域进行深入研究，希望能获得更多有关昆虫呼吸方面的新知。
A new study investigating the respiratory system of insects may have solved a mystery that has intrigued physiologists for decades: why insects routinely stop breathing for minutes at a time.
Challenging previous theories, researchers at UC Irvine and Humboldt University propose that insects such as grasshoppers, moths, butterflies, some types of fruit flies, beetles and bugs close off their respiratory systems periodically to keep out excess oxygen, thus preventing damage to their tissues.
Timothy Bradley, professor of ecology and evolutionary biology at UCI, and Stefan Hetz, assistant professor of physiology at Humboldt University, Germany, report their findings in the Feb. 3 issue of Nature.
The insect respiratory system is designed to accommodate occasions when the insect is active. For example, a grasshopper is most active when it flies. When the grasshopper is inactive and resting, however, it continues to breathe in oxygen at the same high volume it uses while flying. The result is excess internal oxygen that can cause oxidative damage the destruction of biomaterial due to excess oxygen to tissues. To protect their bodies, insects like grasshoppers discontinue breathing.
Two previous models for explaining why insects punctuate their breathing with periods of closure are (1) such discontinuous breathing reduces water loss and (2) it enables insects to rid their bodies of carbon dioxide, respiration byproduct, when the insects are underground. As is true for miners, insects, while underground, are faced with high-carbon-dioxide and low-oxygen amounts, necessitating a better ventilation system. While oxygen is essential for their cells to produce energy, the removal of carbon dioxide from their bodies is equally important to prevent its toxic buildup in tissues.
Even in our own case, our bodies have to supply oxygen to our tissues, but they must also keep out excess oxygen to prevent oxidative damage to the tissues. This damage is closely related to aging. Hence, perhaps, the many anti-oxidative creams flooding the market to combat aging. The concentration of oxygen in the air we breathe is toxic to us. Indeed, fruit flies, which have been studied closely for decades, die sooner from aging in a high-oxygen environment.
Insects take in oxygen through spiracles tubes connected to openings in their sides. In their study, the researchers ed fine tubes into the spiracles of a moth to measure not only how much carbon dioxide the moth released but also the concentration of oxygen in its trachea, the series of tubes that carry air directly to cells for gas exchange. Using a respirometer (an instrument for measuring respiration that consists of a chamber with a flow-through air system), they monitored the moth breathing pattern. The chamber, which housed the moth being studied, was filled first with air that had been freed of carbon dioxide. Next, a device measured when and how much carbon dioxide originated from the insect.
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