No Evidence of Polarization Sensitivity in Freshwater Sunfish from Multi-unit Optic Nerve Recordings

The sensitivities of two species of sunfish (Lepomis gibbosus and Lepomis cyanellus) to the electric field (E-vector) of polarized light were assessed by compound action potential recordings from the optic nerve of live fish. Under white light and long wavelength adapting backgrounds, two cone mechanisms were found with maximum sensitivities in the long wavelength (lambda max approximately 620 nm) and middle wavelength (lambda max approximately 530 nm) regions of the spectrum. In contrast to previous findings (Cameron & Pugh, 1991), no evidence of polarization sensitivity was observed for either species. We conclude from these results that post-larval sunfish do not exhibit polarization sensitivity.