近日,，中科院遺傳與發(fā)育生物學(xué)研究所研究員John Speakman通過(guò)參與國(guó)際合作研究,，解決了長(zhǎng)久以來(lái)困擾科學(xué)界的一個(gè)謎團(tuán)——企鵝為什么不會(huì)飛,？該研究認(rèn)為,，企鵝高效的游泳和潛水行為可能提高了其飛行成本,。相關(guān)研究日前發(fā)表于美國(guó)《國(guó)家科學(xué)院院刊》,。
企鵝為什么在進(jìn)化過(guò)程中喪失了飛行能力,？相關(guān)原因一直以來(lái)都是個(gè)謎,，因?yàn)椴荒茱w行使得企鵝的一些行為看起來(lái)與環(huán)境不相適應(yīng),。例如，為了從棲息地走到海邊,，帝企鵝通常會(huì)花上幾天時(shí)間步行60公里,，它們?nèi)绻茱w的話，則只需要幾個(gè)小時(shí),。
有一種觀點(diǎn)認(rèn)為,，企鵝可能無(wú)法進(jìn)化出既能飛行又能游泳和潛水的雙翼，該假說(shuō)被稱為生物力學(xué)理論,。據(jù)此理論,，企鵝在進(jìn)化過(guò)程中，雙翼越來(lái)越適應(yīng)游泳和潛水,，但也使得其飛行成本越來(lái)越高,，在某些時(shí)候，企鵝無(wú)法維持飛行的成本,，因此就變得不再會(huì)飛,。
為此，來(lái)自加拿大,、美國(guó),、英國(guó)和中國(guó)的科學(xué)家組成聯(lián)合小組，對(duì)海雀科的一種鳥類——海鳩進(jìn)行了觀察,，他們發(fā)現(xiàn),，上述理論或可解釋企鵝為什么不會(huì)飛。
海鳩是一種潛水和游泳行為與企鵝非常類似的海鳥,，不同的是,，海鳩仍然保留了飛行能力。該團(tuán)隊(duì)借助了一種叫做雙標(biāo)水的同位素技術(shù),，在用記錄儀監(jiān)控海鳩行為數(shù)據(jù)的同時(shí)檢測(cè)了海鳩的能量消耗,。
研究結(jié)果顯示，海鳩潛水行為所需的能量低于其他鳥類,，僅次于企鵝潛水行為的效率,。但是，海鳩飛行行為所需的能量,，是其基礎(chǔ)代謝率的31倍,，在所有有報(bào)道的飛行鳥類中是最高的。這種高效潛水和低效飛行行為的結(jié)合很好地印證了生物力學(xué)模型的預(yù)測(cè),。
該文章的第一作者,，來(lái)自加拿大馬尼托巴大學(xué)的研究生Kyle Elliott表示，很顯然,，野生動(dòng)物的結(jié)構(gòu)限制了其功能,，動(dòng)物會(huì)在兩種不同生境的行為中采取折中的辦法,。（生物谷Bioon.com）
生物谷推薦英文摘要：
Proceedings of the National Academy of Sciences DOI：10.1073/pnas.1304838110
High flight costs, but low dive costs, in auks support the biomechanical hypothesis for flightlessness in penguins
Kyle H. Elliotta,1, Robert E. Ricklefsb,1, Anthony J. Gastonc, Scott A. Hatchd, John R. Speakmane,f, and Gail K. Davorena
Flight is a key adaptive trait. Despite its advantages, flight has been lost in several groups of birds, notably among seabirds, where flightlessness has evolved independently in at least five lineages. One hypothesis for the loss of flight among seabirds is that animals moving between different media face tradeoffs between maximizing function in one medium relative to the other. In particular, biomechanical models of energy costs during flying and diving suggest that a wing designed for optimal diving performance should lead to enormous energy costs when flying in air. Costs of flying and diving have been measured in free-living animals that use their wings to fly or to propel their dives, but not both. Animals that both fly and dive might approach the functional boundary between flight and nonflight. We show that flight costs for thick-billed murres (Uria lomvia), which are wing-propelled divers, and pelagic cormorants (Phalacrocorax pelagicus) (foot-propelled divers), are the highest recorded for vertebrates. Dive costs are high for cormorants and low for murres, but the latter are still higher than for flightless wing-propelled diving birds (penguins). For murres, flight costs were higher than predicted from biomechanical modeling, and the oxygen consumption rate during dives decreased with depth at a faster rate than estimated biomechanical costs. These results strongly support the hypothesis that function constrains form in diving birds, and that optimizing wing shape and form for wing-propelled diving leads to such high flight costs that flying ceases to be an option in larger wing-propelled diving seabirds, including penguins.
