Anna Klompen/University of Kansas and Cheryl Ames/Smithsonian Research Collaborator

A close-up view of the jelly’s stinging mucus

Most jellyfish sting when fish or other prey touch their tentacles. But this jelly, called the upside-down jellyfish, stings its victims even when they’re far away. How? It shoots out a stinging, sticky . Scientists recently learned more about how the goo works.

Using microscopes, the scientists discovered that the mucus contains tiny popcorn-shaped structures. These structures, which scientists have named cassiosomes, hold toxic . When the mucus traps small shrimp, the cassiosomes inject the venom to paralyze them. The venom can’t paralyze humans. But if swimmers touch the goo, they feel a burning sensation.  

Next, scientists want to study what triggers the release of the mucus. “There are tons of questions still to be answered,” says biologist Anna Klompen.