Response and place learning in crayfish spatial behavior.

Previous studies have demonstrated that animals use both environmental cues and egocentric information when orienting in mazes or nature. These two strategies have been examined separately in some species, yielding information on the specific properties associated with each. We examined spatial learning in crayfish (Orconectes rusticus) using an apparatus that required animals to orient under four different conditions: using egocentric (response) cues alone, response cues with inconsistent external (place) cues present, place cues with inconsistent response cues present, and place cues with consistent response cues present. Results demonstrated that crayfish could successfully learn a maze task using response cues alone and when external visual and tactile cues provided inconsistent information. Animals were markedly less successful at learning the task using place cues while disregarding inconsistent response information. We also found that more animals learned successfully when response and external cues were presented in a redundant format where both cues indicated the correct turn. Finally, we found that some crayfish were able to learn a single reversal when trained using response information alone and when response and external cues were presented in the redundant format. We consider these results in the light of findings from other species, and ideas on learning strategy properties, ecological relevance of strategies, and the possible role of stress coping style in crayfish learning.