Hydra and Their Tentacles (IMAGE) University of California - Santa Barbara Caption Hydra, left, have the same visual pathway as humans. Their tentacles, right, contain stinging cells (shown here in red) that aid in movement, defense, and predation. Credit David Plachetzki 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.