UCLA

The visual system of freshwater vertebrates shifts photoreceptor sensitivity to longer wavelengths and extends visual sensitivity beyond the range of human vision. One mechanism of enhancing sensitivity to long-wavelength light is to replace the 11-cis retinal chromophore in photopigments with 11-cis 3,4-didehydroretinal. Migratory species of amphibians and salmon can dynamically tune their visual system by altering the balance of 11-cis retinal and 11-cis 3,4-didehydroretinal. Here it is shown that the same process is available in sea lampreys. The ratio of vitamin A2-to-A1 increases as the animals migrate from the open ocean into inland freshwater environments. Suction-electrode recording was used to measure the spectral sensitivity in both adult and juvenile Petromyzon marinus. Primarily, these data show that juvenile lamprey possess a duplex retina. Secondarily, these data demonstrate a strong correlation between the red-shifted light environment of freshwater habitats and the use of the red-shifted vitamin A2 in this primitive vertebrate.