A mechanism of polarized light sensitivity in cone photoreceptors of the goldfish Carassius auratus.

An integrated laser tweezer and microphotometry device has been used to characterize in detail how individual, axially orientated goldfish photoreceptors absorb linearly polarized light. This work demonstrates that the mid-wavelength sensitive members of double cone photoreceptors display axial differential polarization sensitivity. The polarization contrast was measured to be 9.2 +/- 0.4%. By comparison, rod photoreceptors only exhibit isotropic absorbance. These data, combined with the square cone mosaic of double cones in the retina, suggest that intrinsic axial dichroism forms part of the underlying biophysical detection mechanism for polarization vision in this species.