鸟儿怎样找到回家的路?所有人都同意动物能够利用地球磁场来形成一个体内“罗盘”以感应方向的说法,但人们观点的一致性也就到此为止。
一些研究人员提出这样一个观点:磁性是由鸟喙中连接到三叉神经上的磁体来探测的;另一些研究人员则认为,磁性是通过眼睛经由一个复杂的光敏机制来传导的。对后一个观点(即有关眼睛所起作用的观点)的支持,来自对欧洲知更鸟的一项神经外科和行为学研究。在脑中一个被称为“cluster N”的中心有病灶的鸟被发现缺乏磁定向能力。而且至少在这种候鸟中,其喙中假设存在的磁受体在磁性罗盘定向中没有起作用。(生物谷Bioon.com)
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生物谷推荐原始出处:
Nature 461, 1274-1277 (29 October 2009) | doi:10.1038/nature08528
Visual but not trigeminal mediation of magnetic compass information in a migratory bird
Manuela Zapka1, Dominik Heyers1, Christine M. Hein1, Svenja Engels1, Nils-Lasse Schneider1, J?rg Hans1, Simon Weiler1, David Dreyer1, Dmitry Kishkinev1, J. Martin Wild2 & Henrik Mouritsen1
1 AG Neurosensorik/Animal Navigation, IBU, University of Oldenburg, D-26111 Oldenburg, Germany
2 Department of Anatomy, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
Correspondence to: Henrik Mouritsen1 Correspondence and requests for materials should be addressed to H.M.
Magnetic compass information has a key role in bird orientation1, 2, 3, but the physiological mechanisms enabling birds to sense the Earth's magnetic field remain one of the unresolved mysteries in biology2, 4. Two biophysical mechanisms have become established as the most promising magnetodetection candidates. The iron-mineral-based hypothesis suggests that magnetic information is detected by magnetoreceptors in the upper beak and transmitted through the ophthalmic branch of the trigeminal nerve to the brain5, 6, 7, 8, 9, 10. The light-dependent hypothesis suggests that magnetic field direction is sensed by radical pair-forming photopigments in the eyes11, 12, 13, 14, 15 and that this visual signal is processed in cluster N, a specialized, night-time active, light-processing forebrain region16, 17, 18, 19. Here we report that European robins with bilateral lesions of cluster N are unable to show oriented magnetic-compass-guided behaviour but are able to perform sun compass and star compass orientation behaviour. In contrast, bilateral section of the ophthalmic branch of the trigeminal nerve in European robins did not influence the birds' ability to use their magnetic compass for orientation. These data show that cluster N is required for magnetic compass orientation in this species and indicate that it may be specifically involved in processing of magnetic compass information. Furthermore, the data strongly suggest that a vision-mediated mechanism underlies the magnetic compass in this migratory songbird, and that the putative iron-mineral-based receptors in the upper beak connected to the brain by the trigeminal nerve6, 7, 8 are neither necessary nor sufficient for magnetic compass orientation in European robins.