Magnetic orientation in the semi‐terrestrial amphipod, Orchestia cavimana , and its interrelationship with photo‐orientation and water loss

Orchestia cavimana Heller (Amphipoda, Talitridae) were shown to orient to the geomagnetic field as well as to an anisotropic light field. When tested in an isotropic light field the orientation in the geomagnetic field was either in or opposite to the compass direction of the light vector of the anisotropic light field in which the animals had lived before the test, and this orientation was upset predictably by changing the magnetic field with Helmholtz coils. The polarity of the reaction in both magnetic orientation and photo‐orientation was correlated with pre‐experimental water loss. The magnetic orientation of O. cavimana is compared with that of Tenebrio molitor , and its biological significance discussed.