Cassiopea in the Lab (IMAGE) Smithsonian Caption Three Cassiopea, or upside-down jellyfish, from Bonaire, Dutch Caribbean seen from above in the lab at the Department of Invertebrate Zoology in the Smithsonian's National Museum of Natural History. The cloudy matter floating above and to the left of the jellyfish is a mucus that they exude. A team led by scientists at the Smithsonian, the University of Kansas and the U.S. Naval Research Laboratory report in the Feb. 13, 2020 issue of the journal <em>Nature Communications Biology</em> that they have discovered microscopic stinging structures inside the mucus secreted by upside-down jellyfish that cause swimmers and prey to be stung without coming into contact with these jellyfish. Credit Allen Collins and Cheryl Ames Usage Restrictions News-media use of these photos in relation to this study is permitted with attribution. 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.