遊弋在愛爾蘭水域的精靈英語美文

　　Why Do Insects Stop "Breathing"

　　為什麼昆蟲會有規律地停止呼吸?日前，美國及德國的科學家們對這一問題給出了最新的解釋。他們認為，昆蟲之所以會有如此舉動是為了避免吸入對身體有害的過量氧氣。

　　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.

　　據美國“每日科學網站”2月24日報道，透過對昆蟲的呼吸系統進行深入的研究，科學家們或許已經可以揭曉這個在人們心中存在了數十年的謎團。美國加州大學爾灣分校和德國洪堡大學的研究者提出，像蚱蜢、蛾、蝴蝶和果蠅等昆蟲會週期性地關閉它們的呼吸系統，以避免吸入過量的氧氣，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理論發出了挑戰。

　　對於昆蟲有規律地屏住呼吸的問題，以前科學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減少水分的流失;而第二種理論則認為，當昆蟲在地下的時候，這種特別的呼吸方式能使它們從其呼吸作用的副產品——二氧化碳中擺脫出來。因為，當昆蟲處在地面下的時候，它們面臨的是一個高二氧化碳同時低氧的環境。這時，氧氣對昆蟲至關重要，但是從高濃度的二氧化碳中解脫出來，避免在身體組織中產生毒性也同樣具有重要的意義。

　　美國加州大學爾灣分校的生態學及進化生物學教授蒂莫西·布拉德利和德國洪堡大學的生理學助理教授斯特凡·黑茨對這一問題進行了深入研究，並提出了一個更為合理的解釋。他們認為，許多昆蟲關閉氣孔、屏住呼吸是為了避免吸入過量的氧氣。他們將這一研究結果發表在2月份的國際性科技期刊英國著名的《自然》雜誌上。

　　研究顯示，昆蟲在飛行等高度活動的狀態下，會正常呼吸。但是當它們處在不活躍狀態或是休息的時候，他們仍繼續在濃度不變的高氧環境中進行呼吸，其結果就會導致它們吸入過量的氧氣，而體內氧氣過量則會導致昆蟲的身體組織出現氧化損傷。為了使身體免受傷害，一些昆蟲(如蚱蜢等)則會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有規律地間歇性呼吸是為了降低

　　Something Fishy

　　這種30釐米長，身上帶有條紋的cuckoo wrasse魚在愛爾蘭水域很常見。所有的cuckoo wrasse魚剛生下來時都是雌性的，後來其中的一些雌魚在當了幾年母親後，會轉變成雄魚。雄魚會在它的領地裡起支配作用，但等它死了之後，就會有一隻雌魚轉變為雄魚來接替它的位置。

　　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.

　　有些生物學家認為這種手指長的紅色䲁魚(red blenny)只生活在葡萄牙海域。但事實證明，這種小魚的生活範圍要比人們想像的寬闊得多。攝影師布萊恩·史蓋瑞就在愛爾蘭西南海岸附近的'岩石裂縫中，捕捉到了這種小魚的身影。

　　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.

　　在蘇格蘭和愛爾蘭西部沿海，擁有200多隻觸鬚的珍稀海葵讓人們感受到了這種難得一見的美麗。

　　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安全的水平。這種假設可以解釋不同環境下昆蟲的呼吸模式，而以前的理論則無法做到這點。”

　　在研究過程中，科學家用一隻烏桕大蠶蛾的蛹做了試驗。昆蟲沒有肺，所以它們使用通氣孔進行呼吸。科學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。

　　布拉德利教授解釋說，通常昆蟲呼吸系統中的氧氣含量會保持在4-5千帕斯卡，比大氣中的氧氣含量要低4至5倍。

　　透過改變蛾蛹周圍環境的氧含量，研究者發現，在氧氣含量正常的環境中，昆蟲呼吸一段時間，並釋放大量二氧化碳，然後它就會關閉通氣孔，以阻擋更多的氧氣進入。在氧氣含量較低的環境中，昆蟲就會將通氣孔開放的時間延長，關閉的時間縮短。同時，如果在氧氣含量較高的環境中，昆蟲只會在很短的時間裡開啟通氣孔，隨後就將之關閉很長一段時間。換句話說，就是昆蟲能積極地對氧氣含量的多少作出反應，透過開關通氣孔，昆蟲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：“它們的行為告訴我們，它們可以對氧氣含量進行調節。”

　　研究這個問題，就不得不提到氧氣與生物體的關係問題。眾所周知，氧氣是生命之源。但是吸入的氧氣過量也會導致生物體死亡。身體組織暴露在活性很強的氧分子中，會使蛋白質、脂類和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。我們的身體也會向各個組織器官提供氧氣。同樣道理，人們也在盡力避免過量的氧氣對身體帶來的傷害——氧化損傷。這種損傷和人們衰老過程有著緊密的聯絡。或許這就是為什麼市場上會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。空氣中，如果我們呼吸的氧氣濃度過高，這對人體是具有毒性的。事實上，作為分析物件被科學家們反覆研究了數十年的果蠅，如果被置於一個高氧的環境中，就會很快因為衰老而死亡。

　　報道說，科學家們還將在這一領域進行深入研究，希望能獲得更多有關昆蟲呼吸方面的新知。

　　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.

　　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.