If you ___1___ in the Atlantic, you'd flounder on which way to swim. But a hatchling loggerhead turtle would know just where to paddle—by reading the Earth's magnetic field. Scientists knew turtles can ___2___ latitude this way. Because the field varies a lot from north to south. But not east to west. So how do turtles know which side of the Atlantic they're on?
To find out, researchers strapped hatchlings into custom Lycra bathing suits, ___3___ to a tracking unit. They plopped each turtle into a small pool surrounded by magnetic coils. And they ___4___ the magnetic fields of Puerto Rico and the Cape Verde Islands, two points along the turtles' migration, with equal latitudes but different longitudes. The hatchlings swam opposite directions in the two trials—both being the right ones, to stay on the migratory track. The study appears in the journal Current Biology. [Nathan Putman et al., "Longitude Perception and Bicoordinate Magnetic Maps in Sea Turtles"]
The researchers say turtles may calibrate their migratory maps by sensing the magnetic field's intensity, and its inclination to the Earth's surface—a combo that gives each point of the migration a unique signature. As for any human navigators out there, you'll just have to ___5___ for a GPS.
【视听版科学小组荣誉出品】
splashed down pinpoint tethered replicated shell out
假如你一不小心从半空中扑通一声掉进浩瀚大西洋，估计该找不着北了吧。不过幼蠵龟能通过地球磁场来判断该往哪里走。科学家们已经发现海龟能够通过地球磁场判断其所在地的精确纬度，因为地球磁场南北方向差异较大，而东西方向则不然。那海龟是如何知道它们身在大西洋的何处的呢？ 为此，科学家们给小海龟穿上定制的莱卡泳衣以进行追踪，然后将每一头小海龟安置在一个放有线圈的小游泳池中，并利用这些线圈模拟出波多黎各和佛得角群岛附近的磁场，它们所在的纬度相同但经度不同，是小海龟迁徙必经的两个地方。科学家们发现小海龟在不同的磁场中游向相反方向，但都是在迁徙路线上游动，方向判断得相当正确。该研究成果刊登在《当代生物学》杂志上。 科学家们认为海龟是通过感应周围磁场密度以及它们和地球表面的倾角来判断迁徙方向的——这真是标记路标的完美组合啊~要说那千千万万的海员在茫茫大海中该如何是好？买个GPS就OK~