NEUROSENSORY MECHANISMS OF ORIENTIATION TO GEOMAGNETISM

地球磁场提供了一个有用的信息来源， 原则上，可以用来帮助动物定向，迁移或返回， 回到自己的家乡。 从细菌，扁形虫， 软体动物、昆虫、鱼类、鸟类和至少一种哺乳动物表明， 生物体确实使用这种信息来源。 但 关于如何获得这种感觉信息的基本问题， 在神经方面的处理仍然基本上没有答案。 我们最近发现海洋裸鳃类动物 软体动物Tritonia diomedea具有发育良好的行为磁感觉。 我们发现，这种底栖后鳃倾向于在 在失去其他感官线索的情况下，罗盘的方向是可以预测的。 Tritonia是一个研究神经基础的有用模型系统， 行为现象，因为：（一）它的神经系统是由一个 数量相对较少的大的、着色的和可重新识别的神经元， 其中可以从动物到动物单独研究，（ii）它是 研究相对复杂的行为的神经机制是可行的 在几乎完整的动物体内， 技术，（三）以前的工作已经建立了功能作用， 大量的神经元，特别是， 运动和感觉处理。 在这个提议中，我们描述了设计用于（i）进一步证实 行为磁感觉的性质，（ii）隔离和识别 地磁的主要感觉器官和（iii）确定机制 参与了有关磁场的感官信息流向 控制运动方向和速度的神经系统。

The earth's magnetic field provides a useful source of information which can, in principle, be used to help an animal to orient, migrate or to retun to its home territory. Behavioral evidence from bacteria, flatworms, molluscs, insects, fish, birds, and at least one mammal indicates that some organisms do indeed use this source of information. However, the fundamental questions about how this sensory information is obtained and processed in neural terms remain essentially unanswered. This proposal is motivated by our recent finding that the marine nudibranch mollusc Tritonia diomedea has a well-developed behavioral magnetic sense. We have found that this benthic opisthobranch tends to locomote on a predictable compass heading when deprived of other sensory cues. Tritonia is useful model system for studies of the neural basis of behavioral phenomena because: (i) its nervous system is composed of a relatively small number of large, pigmented and reidentifiable neurons some of which can be studied individually from animal to animal, (ii) it is feasible to study the neural mechanisms of relatively complex behavioral acts in the nearly intact animal using both intracellular and extracellular techniques and, (iii) previous work has established the functional roles of a number of neurons, and in particular, neural circuits associated with locomotion and sensory processing. In this proposal we describe experiments designed to (i) confirm further the nature of the behavioral magnetic sense, (ii) isolate and identify the primary sensory organs for geomagnetism and (iii) determine the mechanisms involved in the flow of sensory information about magnetic fields to the neuronal systems that control direction and rate of locomotion.