Sea Butterflies (IMAGE) NOAA Headquarters Caption This close-up image of two pteropods of the species Limacina helicina provides a sense of how fragile the carbonate shells of the tiny sea snails are. Credit Credit: NOAA Ocean Acidification Program 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.