Cnidarian Hydra (IMAGE) University of California - Santa Barbara Caption Opsin genes (blue) are present and expressed in the cnidarian Hydra. Credit David Plachetzki/UCSB Usage Restrictions None License Licensed content 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.