Neuroethology of odour-based navigation in aquatic gastropods

我的长期目标是了解动物如何使用多种导航策略进行移动，重点是腹足类动物基于气味的导航。研究人员花了相当大的精力来了解动物是如何对诱人的气味羽流做出反应的，它们沿着上游爬行，沿着气味来源流动。然而，在自然界中，流动方向经常发生变化。我们对这种流量变化对动物导航的影响知之甚少。我的第一个目标是探索缓慢移动的鼻涕虫和蜗牛如何在两个不同的水平上处理流量变化：一个应该被跟踪，另一个可能应该被忽略。首先，随着大量流动方向的改变，气味羽流也会改变，动物必须跟踪这些转变以找到气味来源。我和我的学生将使用现场视频记录和海流计来探索裸体三叉戟对不同程度的流动的反应，经验地确定鼻涕虫决定整体流动方向的时间尺度。其次，根据水流速度的不同，由不变的整体水流携带的气味羽流将涉及湍流--水流通过基质时产生的流动方向的较小尺度变化。如果是这样的话，动物应该避免跟随这种局部流动的变化，只对潜在的整体流动方向做出反应。在这些实验中，我们将使用淡水蜗牛来测试它们对局部湍流的反应。从对这两个物种的研究中，我们将了解到这些动物如何区分主体流动方向的变化和湍流的变化。我的第二个目标是为探索动物神经系统如何产生这些行为奠定基础。腹足动物实验上的顺从性和更简单的神经系统使我们能够确定单个神经元在线索检测中的作用，以及随后动物爬行的控制机制。然而，在我们对导航中涉及的感觉系统的理解方面仍然存在着很大的差距。因此，我和我的学生将使用各种方法来记录动物感官中神经系统的解剖学。我的第三个目标是专门关注感觉神经元和回路的功能，这些神经元和回路检测和处理圆锥虫的流动方向。这种感觉处理必须作为控制导航的大脑回路的关键输入，然而我们对任何动物的流动方向的检测知之甚少。我们的结果将指导我未来的研究计划，研究腹足类动物产生不同导航策略的神经回路。此外，通过比较整个动物界的结果，我们可以对导航和其他行为背后的神经机制有更广泛的理解。最后，通过这项研究，我的学生将学习到各种基本技能和可移植的技术，他们可以应用于他们的学术或专业生涯。

My long-term goal is to understand how animals use multiple navigation strategies to move, focusing on odour-based navigation in gastropods. Researchers have spent considerable effort to understand how animals respond to attractive odour plumes by crawling upstream, following the flow to an odour source. Yet, in nature, flow directions frequently change. We know much less about the consequences of this flow variability on animal navigation. My first objective is to explore how slow-moving slugs and snails cope with flow variability at two different levels: one that should be tracked, and another that likely should be ignored. First, as bulk flow direction shifts, so do odour plumes, and animals must track these shifts to find odour sources. My students and I will use field video recording and current meters to explore how responsive the nudibranch Tritonia diomedea is to shifting flows of varying degrees, empirically determining the time scale over which the slugs determine bulk flow direction. Second, depending on flow speeds, an odour plume carried by unchanging bulk flow will involve turbulence - smaller scale variations in flow direction generated by water movement across the substrate. If so, the animals should avoid following this local flow variation, responding only to the underlying bulk flow direction. For these experiments, we will use the freshwater snail Lymnaea stagnalis to test their responses to local turbulence. From the work on both species, we will learn how the animals may differentiate between changes in bulk flow direction versus changes from turbulent flow. My second objective is to lay a foundation to explore how the animals' nervous system produces these behaviours. The experimental amenability and simpler nervous system of gastropods allow us to determine the roles of single neurons in cue detection and the subsequent control mechanisms of the animals' crawling. However, there remains a substantial gap in our understanding of the sensory systems involved in navigation. Thus, my students and I will use a variety of methods to document the anatomy of the nervous system in the animals' sense organs. My third objective is to focus specifically on the function of the sensory neurons and circuits that detect and process flow direction in T. diomedea. This sensory processing must serve as a key input into the brain circuits that control navigation, yet we know very little about the detection of flow direction in any animal. Our results will guide future aspects of my research program studying the neural circuits that produce the different navigational strategies in gastropods. Moreover, by comparing results from across the animal kingdom, we can achieve a broader understanding of the neural mechanisms underlying both navigation and other behaviours. Finally, through this research, my students will learn a variety of fundamental skills and transferable techniques they can apply in their academic or professional careers.