非凡而又敏捷的家蠅

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張銳/編譯

Afly can do one thing extremely well: fly. Recently a team of British scientists declared that the common housefly is the most talented aerodynamicist on the planet, superior to any bird, bat,or bee. A housefly can make six turns a second; hover; fly straight up, down, or backward; do somersaults; land on the ceiling; and perform various other show-off maneuvers. And it has a brain smaller than a sesame seed.

Michael Dickinson, who studies fly flight in his lab at Caltech, says the housefly isnt actually the best flier. “Hoverflies are the be-all and end-all,” he says. They can hover in one spot, hurtle through the air to another location, and then race back to their original hovering point—precisely.

Scientists, engineers,and military researchers want to know how creatures with such small brains can do that. Maybe they could reverse-engineer a fly to make a robotic device that could reconnoiter dangerous places,such as earthquake zones or collapsed mines.

Dickinsons laboratory works with fruit flies. Researchers put them in chambers and manipulate the visual field, filming the flies in super-slow motion, 6,000 frames a second. Dickinson is interested in knowing how flies avoid collisions. He has found that certain patterns, such as 90-degree turns,are triggered by visual cues and two equilibrium organs on their backs that function like a gyroscope.

Flies have only a dozen muscles for maneuvering, but theyre loaded with sensors. In addition to their compound eyes, which permit panoramic imagery and are excellent at detecting motion, they have wind-sensitive hairs and antennae. They also have three light sensors,called ocelli, on the tops of their heads, which tell them which way is up. Roughly two-thirds of a flys entire nervous system is devoted to processing visual images. They take all this sensory data and boil it down to a few basic commands, such as “go left” and “go right”.

Given that flies have evolved for hundreds of millions of years ( and that they were the first animals to take to the air ), we shouldnt be surprised that theyre such good fliers. “They just dont have brains like ours. Studying flies,” says Dickinson,“is like traveling to another planet.”

一只家蠅能把一件事做得出奇得好，那就是：飛行。最近，一組英國科學家宣布，普通的家蠅是地球上最天才的空氣動力學家，它比任何的鳥、蝙蝠或蜜蜂都要高明許多。一只家蠅能在一秒鐘之內做6個旋轉動作；它能在空中旋停；向上直飛、向下直飛、向后直飛；它能翻筋斗；降落在天花板上；而且它還能做出各種各樣炫目的飛行動作。而它的大腦比一粒芝麻籽還要小。

邁克爾·迪肯森一直在加利福尼亞理工學院的實驗室里研究家蠅的飛行。他說，家蠅事實上并不是飛行技能最好的飛行動物，他說：“食蚜虻才是最高明的飛行動物。”它們能旋停在空中的一個點上，然后又在空中猛地沖到另一個地點，之后再全速飛回到它們原來所旋停的那個點上，做得非常精確。

科學家、工程師以及軍事研究人員都想知道，大腦如此之小的動物是怎樣做到這一點的。也許他們可以通過對家蠅的研究對它們進行仿制，制造出一個儀器，可以用它來勘察危險的地區，如地震帶或坍塌的礦井地帶。

迪肯森的實驗室是用果蠅作為研究對象的。研究人員把它們放在小室中，并且通過對視野的巧妙處理，用每秒6000個畫面的方式，給果蠅拍攝電影。迪肯森很想知道蠅類是怎樣避免碰撞的。他發現，某些模式，如90°轉彎這個飛行動作，就是被看得見的信號所觸發的，在它們的脊背上有兩個平衡器官，其功能相當于一個陀螺儀。

家蠅只有12塊肌肉可以用來做動作，但它們的身上卻布滿了感覺器官。它們的復眼能讓它們看到全景的畫像，并且在探測動作方面，它們的復眼也是很優秀的。除了復眼之外，它們還有對風敏感的毛發和觸須。它們還有三個光感覺器官，叫單眼，就長在它們的頭頂上。這三個感覺器官能告訴它們哪個方向是“上”。一只家蠅的整個神經系統大約有三分之二是用來處理視覺圖像的。它們處理所有的這些感覺數據，并且將之壓縮簡化為幾個基本的指令，比如“向左飛”或“向右飛”。

家蠅已經進化了很多億年（而且它們是最先學會飛行的動物），考慮到這一點，我們就不應該驚奇它們是飛行技能如此好的飛行動物。迪肯森說：“它們只是沒有同我們一樣的大腦。研究家蠅的過程就好像是去往另一個行星的旅程。”