Geomagnetic field detection by the western Atlantic spiny lobster,Panulirus argus

Abstract

Conditioning experiments were conducted to test the ability of western Atlantic spiny lobsters (Panulirus argus) to orient using geomagnetic cues. Lobsters were trained and tested in a rotatable circular orientation apparatus in which they could enter tunnels aligned with one of six compass bearings. In initial experiments animals were positively reinforced for entering the tunnel at magnetic north and negatively reinforced for entering all other tunnels. While deprived of all known or suspected guideposts other than the geomagnetic field, conditioned lobsters entered tunnels aligned with the north‐south magnetic axis significantly more often than other tunnels. However, the animals did not demonstrate the ability to discriminate north from south under the experimental conditions. To confirm that location of the north‐south axis was mediated by magnetic field detection, a pair of conditioned lobsters was subjected to trials in an altered magnetic field in which magnetic north was rotated 60° counterclockwise. The axial preference of the lobsters immediately shifted to the new north‐south magnetic axis. These initial experiments provide evidence that spiny lobsters can derive directional information from the magnetic field of the earth.