Neuroethology of navigation in Tritonia

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My overall goal is to understand how animals use multiple navigation strategies to move.  My students and I will tackle this problem by focusing on odour-based navigation in the sea slug Tritonia diomedea. Considerable effort has been spent understanding how animals respond to attractive odour plumes to find odour sources.  A variety of studies have shown that the slugs and other animals do no use odours alone for this process.  Instead, the presence of odours stimulate the animals to crawl upstream, following the flow to the 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 two objectives are to explore how the slugs cope with flow variability at two different levels: one level that should be tracked in order to reach the odour source, and another level that should probably be ignored for successful navigation. First, as bulk flow direction changes in a habitat, so too do odour plumes.   Animals must track these changes in the flow carrying the odour plume to find odour sources. My students and I will use field video recordings to explore how responsive Tritonia is to shifting flows of varying degrees. Second, inside an odour plume carried by unchanging bulk flow, water movement across the sea floor generates smaller scale variations in flow direction. This turbulence does not provide useful information for finding the odour source, and should be ignored.  The slugs show movements that suggest they may be adapted to cope with the turbulence, but there has been no experimental verification of this possibility.  Consequently, I will also test for how responsive the slugs are to finer flow variations, and thus gain insight into how the slugs may differentiate between changes in bulk flow direction versus changes from turbulent flow. My final objective is to lay a foundation for exploration of how the slugs' nervous system produces these behaviours. The experimental amenability and simpler nervous system of Tritonia allow experiments to test the roles of single neurons in cue detection and the subsequent control mechanisms of the slugs' crawling. I propose to study the structure and function of the sensory components of the nervous system, as well as test which neurons directly control turns stimulated by odours in flow. These two components serve as the input and output respectively for the circuit of neurons that controls navigation, and the results will guide future work studying how that circuit functions to produce the different navigational strategies. More generally, by comparing these results to those from across the animal kingdom, we can achieve a broader understanding of the neural mechanisms underlying navigation behaviour. Moreover, the methods used here are applicable to other areas of neuroscience, and my students will acquire valuable skills as they continue in academic or professional careers.