An intra-species demonstration of the independence of distance and time in turn alternation of the terrestrial isopod, Porcellio scaber.
In a study of turn alternation in the terrestrial isopod Porcellio scaber (woodlouse), smaller individuals (<11 mm long) took significantly longer to traverse a 60-mm open-ended post-forced-turn runway following a 90 degrees forced turn, than larger subjects (>11 mm long). However, there were no significant differences between the two groups in their probability of alternating, or in the magnitude of alternating turns as reflected in the size of the free-turn angles they turned on emerging from the runway. Nor was there a significant relationship for either group between the time taken to traverse the runway and either the probability of alternating or the size of a free-turn angle. In a second experiment, significant alternation occurred after woodlice emerged from runways that were 30 and 60 mm long, but not when they were 100 or 145 mm long. Their free-turn angles also became smaller as the runway length increased. Overall, the results of the three experiments supported the long-held view that, for reasons not yet understood, distance and time cannot necessarily be equated in the determination of invertebrate turn alternation.
Hughes
Robert N
RN
Department of Psychology, University of Canterbury, Private Bag 4800, Christchurch, New Zealand. rob.hughes@canterbury.ac.nz
D000818:Animals; D002755:Choice Behavior; D004215:Distance Perception / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology*; D033321:Isopoda / Q000502:physiology*; D018782:Maze Learning / Q000502:physiology; D013037:Spatial Behavior / Q000502:physiology*; D013998:Time Perception / Q000502:physiology*