WYETH, R.C.; WILLOWS, A.O.D.; University of Washington; University of Washington: Integration of multiple sensory cues by the nudibranch mollusk, Tritonia diomedea, during navigation through its natural habitat

Animals use a variety of senses to navigate through their environment. How do they integrate multiple senses to direct movement? The nudibranch Tritonia diomedea is an excellent candidate for investigating mechanisms of sensory integration and subsequent behavior. Although neurophysiological and behavioral aspects of mechano-, chemo-, and magnetosensation have all been investigated in this animal, little is known about how these different sensory systems are used in nature. We are characterizing the orientation and navigation of T. diomedea in their native sea pen beds using underwater time-lapse video, and then attempting to correlate the observed movements with sensory cues which may be guiding the animals. Previous preliminary results indicated T. diomedea likely uses water currents to search out upstream conspecifics before mating. Qualitative observations suggested that in certain situations, however, other cues are used to guide the animals while they crawl. We quantified, in detail, T. diomedea orientation and movements with respect to water flow and the Earth’s magnetic field both with and without upstream conspecifics to determine if, during episodes of �unreliable� information from water flow direction, they resort to magnetic bearings to continue their search for a mate. Our results suggest T. diomedea used neither currents nor an internal compass exclusively to guide their movements. T. diomedea probably integrates information from odors, averaged water flow directions, and the earth�s magnetic field to help guide itself as it moves about its habitat.