Department of Biology, Coker Hall, CB#3280, University of North Carolina, Chapel Hill, NC 27599, USA.
J Exp Biol. 2011 Aug 1;214(Pt 15):2504-8. doi: 10.1242/jeb.055921.
Young loggerhead sea turtles (Caretta caretta) from the east coast of Florida, USA, undertake a transoceanic migration around the North Atlantic Gyre, the circular current system that flows around the Sargasso Sea. Previous experiments indicated that loggerhead hatchlings, when exposed to magnetic fields replicating those that exist at five widely separated locations along the migratory pathway, responded by swimming in directions that would, in each case, help turtles remain in the gyre and advance along the migratory route. In this study, hatchlings were exposed to several additional magnetic fields that exist along or outside of the gyre's northern boundary. Hatchlings responded to fields that exist within the gyre currents by swimming in directions consistent with their migratory route at each location, whereas turtles exposed to a field that exists north of the gyre had an orientation that was statistically indistinguishable from random. These results are consistent with the hypothesis that loggerhead turtles entering the sea for the first time possess a navigational system in which a series of regional magnetic fields sequentially trigger orientation responses that help steer turtles along the migratory route. By contrast, hatchlings may fail to respond to fields that exist in locations beyond the turtles' normal geographic range.
来自美国佛罗里达州东海岸的年轻红海龟（Caretta caretta）进行跨越大西洋环流（环绕马尾藻海的圆形洋流系统）的远洋洄游。之前的实验表明，当暴露在模拟迁徙路径上五个相距甚远的位置的磁场中时，红海龟的幼龟会做出反应，朝着有助于它们留在环流中并沿着迁徙路线前进的方向游动。在这项研究中，幼龟还暴露在环流北部边界内外的几个额外磁场中。幼龟对环流内部的磁场做出反应，朝着每个位置的迁徙路线方向游动，而暴露在环流以北的磁场中的海龟的方向与随机方向没有统计学上的区别。这些结果与以下假设一致：首次进入大海的红海龟拥有一种导航系统，其中一系列区域磁场依次触发定向反应，帮助海龟沿着迁徙路线前进。相比之下，幼龟可能无法对超出其正常地理范围的位置的磁场做出反应。
