Meeting Abstract

P1.103  Sunday, Jan. 4  The influence of odor cues, water flow, & magnetic fields on the orientation of the sea slug Tritonia diomedea JONES, AJ*; MURRAY, JA; CAIN, SD; WYETH, RC; U. Montana; Cal. State. U. East Bay; E. Oregon U.; St. Francis Xavier U. james.murray@mac.com

Tritonia diomedea is suitable for studying the integration of multiple sensory cues and their role in navigation because it has as a well-characterized central nervous system with re-identifiable neurons & consistent orientation behaviors. Several sensory stimuli that have been previously shown to influence orientation behavior (rheotactic, olfactory, magnetic) were manipulated in order to test the role each plays in influencing the slugs navigation towards food. We elicited foraging behavior in starved T. diomedea placed in a flow tank downstream from prey (Ptilosarcus gurneyi). We hypothesized that after orienting to a food odour plume and then removing the source of the odor, Tritonia would use geomagnetic cues to maintain a bearing towards the original odor source location in the absence of either olfactory and/or rheotactic cues (‘orienteering’ hypothesis). As found previously, odors played a gating/motivational role in foraging behavior, and rheotactic stimuli helped orient the animal upstream toward the odor source. Geomagnetic field reversals had no apparent effect on slug movements compared to controls, with or without flow and with or without odors. Thus we found no evidence in support of the orienteering hypothesis. We also observed a novel mode of navigation, cross-current ‘casting’ or ‘counterturning’ (successive left and right turns), following odor removal. Before removal of the odor & flow, turning radius and angular speed were relatively smaller. After odor removal, with or without water flow, the turns were more frequent, with a shorter turning radius, and a lower angular speed.