Ray Vision (image) Molecular Biology and Evolution (Oxford University Press) Share Print E-Mail Caption All cartilaginous fishes, similar to the marine mammals, have lost the SWS1 and SWS2 opsin genes. Sharks and rays do contain both rod and cone photoreceptors; however rays were found to possess two cone opsin genes. Credit Nathan Hart, Macquarie University Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.