Extraocular perception of polarized light by orienting salamanders

Spatial orientation corresponding to the bearing of thee-vector of linearly polarized light can be demonstrated in sighted and eyeless salamanders (Ambystoma tigrinum) trained under linearly polarized light. However, if opaque polyethylene plastic is inserted over the skull of these animals, whether they are sighted or eyeless, orientation is uniform within the test arena. Bidirectional oriented movement is restored in both groups, however, when transparent plastic is substituted in the same animals. A discussion of the possible mechanism for perception of polarized light by extraocular photoreceptors (EOPs) is given.