OLFACTION AND SELECTIVE ASSOCIATION IN THE EARTHWORM, LUMBRICUS-TERRESTRIS

Parameters of Lumbricus terrestris behavior and learning in a T-maze are explored by comparing the animals' use of odor as a cue with their use of more traditional stimuli. Available stimuli are a volatile odor, inclination of the maze, and light-shadow at the choice point-as well as kinesthetic-tactile stimuli. It is found that L. terrestris can use odor to choose a specified exit on the first trial. However, more than a taxis is involved. Behavior over trials is characterized by a rapid decrease in choice speed when the consequences of at least one alternative are noxious (saline), and by a rapid increase in choice speed when the consequence of neither alternative is noxious. Contrasting above and below threshold intensities of the odor stimulus, with and without noxious consequences, reveals that only odor permits rapid association of cue and consequence. The specificity and rapidity of the behavior changes found with odor suggests selective association must be considered as a factor in earthworm learning. © 1979 Academic Press, Inc.