LEARNING OF ESCAPE DIRECTION IN IDOTEA-BALTICA

Experiments on solar orientation have been carried out on adult and la boratory born individuals of the marine isopod Idotea baltica. A plexi glass bowl, with the landscape screened from view, was used for the re leases (individual and group). In the majority of releases there is a bimodal tendency in the orientation along the y axis. Results demonstr ate that the capacity to assume an ecologically efficient direction is not determined genetically and is liable to weaken after the animals are kept for approximately a week in the laboratory. Once Idotea balti ca has learned the Y axis escape direction, it can rapidly modify it i f any changes occur in the orientation of the sea-land axis.