Seeing Starfish (2 of 3) (IMAGE) Society for Experimental Biology Caption The starfish compound eye (red cups) is seen at the tip of the arm. Each red cup corresponds to a single optical unit, ommatidium, in an arthropod compound eye. Credit Dan-Erik Nilsson, Lund University 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.