游弋在愛(ài)爾蘭水域的精靈英語(yǔ)美文
Why Do Insects Stop "Breathing"
為什么昆蟲(chóng)會(huì )有規律地停止呼吸?日前，美國及德國的科學(xué)家們對這一問(wèn)題給出了最新的解釋。他們認為，昆蟲(chóng)之所以會(huì )有如此舉動(dòng)是為了避免吸入對身體有害的過(guò)量氧氣。
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.
為什么昆蟲(chóng)會(huì )有規律地停止呼吸?日前，美國及德國的科學(xué)家們對這一問(wèn)題給出了最新的解釋。他們認為，昆蟲(chóng)之所以會(huì )有如此舉動(dòng)是為了避免吸入對身體有害的過(guò)量氧氣。
據美國“每日科學(xué)網(wǎng)站”2月24日報道，通過(guò)對昆蟲(chóng)的呼吸系統進(jìn)行深入的研究，科學(xué)家們或許已經(jīng)可以揭曉這個(gè)在人們心中存在了數十年的謎團。美國加州大學(xué)爾灣分校和德國洪堡大學(xué)的研究者提出，像蚱蜢、蛾、蝴蝶和果蠅等昆蟲(chóng)會(huì )周期性地關(guān)閉它們的呼吸系統，以避免吸入過(guò)量的氧氣，從而使自己的身體組織免受傷害。這一結論則向以前的相關(guān)理論發(fā)出了挑戰。
對于昆蟲(chóng)有規律地屏住呼吸的問(wèn)題，以前科學(xué)家們曾提出了兩種解釋。
一種理論認為，這種間斷地不連續地呼吸可以幫助昆蟲(chóng)減少水分的流失;而第二種理論則認為，當昆蟲(chóng)在地下的時(shí)候，這種特別的呼吸方式能使它們從其呼吸作用的副產(chǎn)品——二氧化碳中擺脫出來(lái)。因為，當昆蟲(chóng)處在地面下的時(shí)候，它們面臨的是一個(gè)高二氧化碳同時(shí)低氧的環(huán)境。這時(shí)，氧氣對昆蟲(chóng)至關(guān)重要，但是從高濃度的二氧化碳中解脫出來(lái)，避免在身體組織中產(chǎn)生毒性也同樣具有重要的意義。
美國加州大學(xué)爾灣分校的生態(tài)學(xué)及進(jìn)化生物學(xué)教授蒂莫西·布拉德利和德國洪堡大學(xué)的生理學(xué)助理教授斯特凡·黑茨對這一問(wèn)題進(jìn)行了深入研究，并提出了一個(gè)更為合理的解釋。他們認為，許多昆蟲(chóng)關(guān)閉氣孔、屏住呼吸是為了避免吸入過(guò)量的氧氣。他們將這一研究結果發(fā)表在2月份的國際性科技期刊英國著(zhù)名的《自然》雜志上。
研究顯示，昆蟲(chóng)在飛行等高度活動(dòng)的狀態(tài)下，會(huì )正常呼吸。 但是當它們處在不活躍狀態(tài)或是休息的時(shí)候，他們仍繼續在濃度不變的高氧環(huán)境中進(jìn)行呼吸，其結果就會(huì )導致它們吸入過(guò)量的氧氣，而體內氧氣過(guò)量則會(huì )導致昆蟲(chóng)的身體組織出現氧化損傷。為了使身體免受傷害，一些昆蟲(chóng)(如蚱蜢等)則會(huì )選擇間歇性停止呼吸這一做法。
對此，布拉德利教授表示：“我們認為大部分昆蟲(chóng)有規律地間歇性呼吸是為了降低
Something Fishy
這種30厘米長(cháng)，身上帶有條紋的cuckoo wrasse魚(yú)在愛(ài)爾蘭水域很常見(jiàn)。所有的cuckoo wrasse魚(yú)剛生下來(lái)時(shí)都是雌性的，后來(lái)其中的一些雌魚(yú)在當了幾年母親后，會(huì )轉變成雄魚(yú)。雄魚(yú)會(huì )在它的領(lǐng)地里起支配作用，但等它死了之后，就會(huì )有一只雌魚(yú)轉變?yōu)樾埕~(yú)來(lái)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.
有些生物學(xué)家認為這種手指長(cháng)的紅色鳚魚(yú)(red blenny)只生活在葡萄牙海域。但事實(shí)證明，這種小魚(yú)的生活范圍要比人們想像的寬闊得多。攝影師布萊恩·史蓋瑞就在愛(ài)爾蘭西南海岸附近的'巖石裂縫中，捕捉到了這種小魚(yú)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.
在蘇格蘭和愛(ài)爾蘭西部沿海，擁有200多只觸須的珍稀�？屓藗兏惺艿搅诉@種難得一見(jiàn)的美麗。
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)
體內的氧氣濃度，以保證生理上的安全。它們充分減少氣體交換頻率，使體內的氧量保持在一個(gè)安全的水平。這種假設可以解釋不同環(huán)境下昆蟲(chóng)的呼吸模式，而以前的理論則無(wú)法做到這點(diǎn)�！�
在研究過(guò)程中，科學(xué)家用一只烏桕大蠶蛾的蛹做了試驗。昆蟲(chóng)沒(méi)有肺，所以它們使用通氣孔進(jìn)行呼吸�？茖W(xué)家把導管插入到蛾蛹的通氣孔中，以測量它排放的二氧化碳量及吸入的氧氣含量。研究者還使用呼吸計(一種測量呼吸作用的儀器respirometer)監測飛蛾的呼吸形態(tài)。
布拉德利教授解釋說(shuō)，通常昆蟲(chóng)呼吸系統中的氧氣含量會(huì )保持在4-5千帕斯卡，比大氣中的氧氣含量要低4至5倍。
通過(guò)改變蛾蛹周?chē)h(huán)境的氧含量，研究者發(fā)現，在氧氣含量正常的環(huán)境中，昆蟲(chóng)呼吸一段時(shí)間，并釋放大量二氧化碳，然后它就會(huì )關(guān)閉通氣孔，以阻擋更多的氧氣進(jìn)入。在氧氣含量較低的環(huán)境中，昆蟲(chóng)就會(huì )將通氣孔開(kāi)放的時(shí)間延長(cháng)，關(guān)閉的時(shí)間縮短。同時(shí)，如果在氧氣含量較高的環(huán)境中，昆蟲(chóng)只會(huì )在很短的時(shí)間里打開(kāi)通氣孔，隨后就將之關(guān)閉很長(cháng)一段時(shí)間。換句話(huà)說(shuō)，就是昆蟲(chóng)能積極地對氧氣含量的多少作出反應，通過(guò)開(kāi)關(guān)通氣孔，昆蟲(chóng)可以使體內的氧氣和二氧化碳含量保持在相當穩定的水平。這在某種程度上顯示它們能夠自行衡量氧氣的多少。布拉德利教授說(shuō)：“它們的行為告訴我們，它們可以對氧氣含量進(jìn)行調節�！�
研究這個(gè)問(wèn)題，就不得不提到氧氣與生物體的關(guān)系問(wèn)題。眾所周知，氧氣是生命之源。但是吸入的氧氣過(guò)量也會(huì )導致生物體死亡。身體組織暴露在活性很強的氧分子中，會(huì )使蛋白質(zhì)、脂類(lèi)和DNA受損，促使細胞死亡、加快衰老。
對此，研究者表示，即使在我們的身體中，這種情況也是存在的。我們的身體也會(huì )向各個(gè)組織器官提供氧氣。同樣道理，人們也在盡力避免過(guò)量的氧氣對身體帶來(lái)的傷害——氧化損傷。這種損傷和人們衰老過(guò)程有著(zhù)緊密的聯(lián)系�；蛟S這就是為什么市場(chǎng)上會(huì )出現眾多的抗氧化護膚品的原因——人們也在想盡一切辦法抵抗衰老�？諝庵�，如果我們呼吸的氧氣濃度過(guò)高，這對人體是具有毒性的。事實(shí)上，作為分析對象被科學(xué)家們反復研究了數十年的果蠅，如果被置于一個(gè)高氧的環(huán)境中，就會(huì )很快因為衰老而死亡。
報道說(shuō)，科學(xué)家們還將在這一領(lǐng)域進(jìn)行深入研究，希望能獲得更多有關(guān)昆蟲(chóng)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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