Ultraviolet transmission by the ocular media of goldfish: implications for ultraviolet photosensitivity in fishes

Abstract

Spectral transmittance of goldfish (n = 10) ocular media was measured in the 320- to 750-nm range with a spectrophotometer modified to eliminate problems associated with chromatic aberration and beam scattering. Absolute transmittance in the visible range was 0.8 at 400 nm and 0.95 at 750 nm. Transmittance below 400 nm dropped off to 0.3 at 340 nm and exhibited high variability between individuals. Linear regression analysis showed that ultraviolet (UV) transmittance was not systematically related to age, body weight, standard length, or ocular diameter of fish. Low UV transmittance of the ocular media was shown to influence the UV peak spectral sensitivity by narrowing the action spectrum on the short wavelength side and displacing the UV peak sensitivity to longer wavelengths. Correcting spectral sensitivity curves for ocular media transmittance resulted in agreement with λ_max 370 nm absorption spectrum.