WYETH, Russell C.; Dalhousie University: Modeling navigation in the sea slug Tritonia diomedea: strategies for finding odor sources in variable flow.

Animals navigate by integrating multiple environmental sensory cues to produce directed locomotion. From analysis of crawling patterns in the field and laboratory experiments, we know the nudibranch mollusc Tritonia diomedea uses a combination of odor cues and flow direction to guide navigation relative to targets of interest (prey, predators, and mates). However, it is not clear what navigational cues are used in the absence of odors. Theoretical considerations suggest a range of crawling strategies may be optimal depending on flow variability and how long ago odors were last detected. I use a simple numerical model of T. diomedea movements to explore the slugs� navigational options. Using real current data and locomotory parameters from field observations, I compare the success of different stategies at finding odor sources. In particular, I test the possibility that the slugs� magnetosensation might help them find odor sources following changes in current flow. These results will help guide both neuroethological and behavioural experimentation, contributing to a more complete picture of how mechanosensation, chemosensation, and possibly magnetosensation are integrated to produce directed locomotion in T. diomedea.