Intraspecific variation of spectral sensitivity in threespine stickleback (Gasterosteus aculeatus) from different photic regimes

Abstract

To examine the influence of the spectral characteristics of underwater light on spectral sensitivity of the ON and OFF visual pathways, compound action potential recordings were made from retinal ganglion cells of threespine stickleback from different photic regimes. In fish from a red-shifted photic regime (λP₅₀ 680 nm for downwelling light at 1m), peak sensitivity of both the ON and OFF pathways was limited to long wavelength light (λ_max 600–620). In contrast, the ON pathway of fish from a comparatively blue-shifted (λP₅₀ 566 nm) photic regime exhibited sensitivity to medium (λ_max 540–560) and long (λ_max 600 nm) wavelengths, while the OFF pathway exhibited peak sensitivity to only medium (λ_max 540 nm) wavelength light. In a third population, where the the ambient light is moderately red-shifted (λP₅₀ 629 nm), the ON pathway once again exhibited only a long wavelength sensitivity peak at 620 nm, while the OFF pathway exhibited sensitivity to both medium (λ_max 560 nm) and long (λ_max 600–620 nm) wavelength light. These findings suggest that the photic environment plays an integral role in shaping spectral sensitivity of the ON and OFF pathways.