Gagliardo Anna, Ioalè Paolo, Savini Maria, Wild Martin
Dipartimento di Biologia, University of Pisa, Via A. Volta 6, Pisa, Italy.
J Exp Biol. 2008 Jul;211(Pt 13):2046-51. doi: 10.1242/jeb.017608.
Anatomical evidence and conditioning experiments have recently suggested that magnetoreceptors are located in the upper beak of homing pigeons, where they are innervated by the ophthalmic branch of the trigeminal nerve. These findings have raised the issue of whether the trigeminally mediated magnetoreception is involved in the navigational mechanisms of homing pigeons. Recent data have shown that, in inexperienced pigeons, section of the ophthalmic branch of the trigeminal nerve does not impair navigational abilities, whereas the navigational performance of inexperienced pigeons is disrupted after section of the olfactory nerve. Nevertheless, the issue of whether the stimuli available during development of the navigational mechanism can influence the types of cues used in determining the direction of displacement remains unresolved. To address this issue, we surgically deprived young pigeons of either olfactory or trigeminally mediated magnetic information, and then later tested their navigational abilities subsequent to an intensive training flight program of up to 10 km in different directions. The birds deprived of trigeminally mediated magnetic information when young developed navigational abilities at the same level as intact control pigeons, whereas the olfactory deprived pigeons displayed randomly scattered initial orientation and poor homing performance. Our data show that olfactory cues are needed for the development of navigational abilities from unfamiliar locations and that the lack of magnetic information does not affect the development of homing abilities.
解剖学证据和条件实验最近表明，磁感受器位于信鸽的上喙，由三叉神经的眼支支配。这些发现引发了一个问题，即三叉神经介导的磁感受是否参与信鸽的导航机制。最近的数据表明，在未经历过训练的鸽子中，切断三叉神经的眼支不会损害其导航能力，而切断嗅神经后，未经历过训练的鸽子的导航表现会受到干扰。然而，导航机制发育过程中可用的刺激是否会影响用于确定位移方向的线索类型这一问题仍未得到解决。为了解决这个问题，我们通过手术剥夺了幼鸽的嗅觉或三叉神经介导的磁信息，然后在进行了长达10公里不同方向的强化训练飞行计划后，测试它们的导航能力。幼年时被剥夺三叉神经介导磁信息的鸽子，其发展出的导航能力与完整的对照鸽子处于同一水平，而被剥夺嗅觉的鸽子则表现出初始方向随机分散且归巢表现不佳。我们的数据表明，从陌生地点发展导航能力需要嗅觉线索，而缺乏磁信息不会影响归巢能力的发展。
