Light-dependent orientation responses in animals can be explained by a model of compass cue integration

Kenneth Kragh Jensen (1)

1 SDU - University of Southern Denmark

The magnetic compass sense of animals is currently thought to be based on light-dependent processes like the proposed radical pair mechanism. In accordance, many animals show orientation responses that depend on light. However, the orientation responses depend on the wavelength and irradiance of monochromatic light in rather complex ways that cannot be explained directly by the radical pair mechanism. Here, a radically different model is presented that can explain a vast majority of the complex observed light-dependent responses. The model put forward an integration process consisting of simple lateral inhibition between a normal functioning, light- magnetic compass (e.g. magnetite based) and a vision based skylight color gradient compass that misperceives compass cues in monochromatic light. Integration of the misperceived color compass cue and the normal magnetic compass not only explains most of the categorically different light-dependent orientation responses and their sequential occurrence, but also shows a surprisingly good fit to how well the animals are oriented (r-values) under light of different wavelength and irradiance. The model parsimoniously suggests the existence of a single magnetic compass in birds (probably based on magnetite) and explains the light-dependency as simple interference with another, vision based compass.

Mots clés: Magnetoreception; Monochromatic light; Light-dependent orientation responses; Radical pair mechanism; Magnetite

Kenneth Kragh Jensen. Light-dependent orientation responses in animals can be explained by a model of compass cue integration. Journal of Theoretical Biology, 2009, 262 (1), pp.129. ⟨10.1016/j.jtbi.2009.09.005⟩. ⟨hal-00554644⟩