Maze Learning and Recall in Weakly Electric Fish, Mormyrus rume proboscirostris Boulenger 1898 (Teleostei, Mormyridae): Sensory Bases
Animals use navigational strategies ranging from taxes, landmark and compass orientation, and path integration to cognitive maps. The debate concerning the use of mapping strategies, or less complex mechanisms such path integration, landmark orientation, or dead reckoning is far from settled. Nocturnal weakly electric fish (family Mormyridae) leave their daytime hiding places at night to forage for food and return at dawn. Thus, these fish provide an excellent model to explore their navigational strategies. The present studies explore these strategies using a novel paradigm: after learning to swim through a maze (acquisition), the maze barriers are removed and the fish allowed to swim through the empty arena (recall). The recall trajectory is an indicator of the fish's navigational strategy. The role of active electrosensing, sight, and lateral line input is explored. Acquisition deteriorates with the number of senses available. Fish with all three senses intact learned the fastest (7 days), whereas fish with these three senses eliminated needed 18 days suggesting still other sensory modalities at work. Recall, however, is similar across groups suggesting independence of external input. Allowing trained fish to start from a novel location provided evidence for path integration and dead reckoning, but not cognitive mapping. When the arena provided additional visual or electric landmarks during acquisition, during recall with the maze removed but the landmarks left in place, intact fish did not attend to visual but strongly to electric landmarks (array of Plexiglas and Aluminum cubes). However, when the electric landmarks were relocated or removed prior to recall, fish again became independent of 'unreliable' external cues.
City University of New York - Graduate Center
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