![]() ![]() We don't know yet if upside-down jellyfish release more cassiosomes in response to certain disturbances or at certain times of the day, Collins added. "When it's low tide … obviously, there's less water around - and you're closer to the jellyfish, and you're more likely to disturb them," said co-author Allen Collins, a zoologist at the Smithsonian's National Museum of Natural History and the National Oceanic and Atmospheric Administration's National Systematics Laboratory. So, how can you avoid swimming through a toxic minefield on your next trip to the Florida Keys? "However, this upside-down jellyfish actually builds a around itself, a defense layer of mucus that contains these cassiosome bombs." "Nematocytes are found mostly on the jellyfish tentacles," said Lotan, who was not involved in the new study. in Cassiopea demonstrates an unexpected way of organization," Tamar Lotan, head of the Department of Marine Biology at the University of Haifa in Israel, told Live Science in an email. "The discovery of motile, nematocyte-containing cellular structures. The team named the free-wheeling spheres "cassiosomes," after the Cassiopea genus. These cilia wave in the water and act as tiny propellers that send the spheres spinning off in every direction. In addition to stinging nematocytes, cells covered in hairlike threads called cilia stud the surface of the spheres. Stinging cells called nematocytes coat the outermost layer of the bumpy spheres when touched, these cells leak venom from long, stringy structures on their surfaces, stinging unwary creatures that run into them. By analyzing the molecules and proteins in the spheres, Ames' team confirmed that the spheres came from the jellyfish and were dispersed from spoon-shaped pads on the animals' arms.Ĭlose-up of a cassiosome (Image credit: Allen Collins and Cheryl Ames) A minefield of mucus and toxic "bombs" The team uncovered one stray study from 1908 that mentioned the strange spheres, but those researchers had wrongly identified the structures as parasites of the jellyfish. "None of us could figure out immediately what they were." "We were really kind of in awe and shock, and saying, 'What are these? Has anyone seen these?'" Ames said. They spotted tiny, jelly-filled spheres floating within the fluid that appeared to be packed with cells and algae. To find out if these oddball jellies were the culprit, the researchers looked at samples of the jellies' mucus under high-resolution microscopes. With the mystery still unsolved, the scientists realized that, whenever they were stung, they were swimming near upside-down jellyfish at low tide, while the jellies pumped out murky clouds of mucus. Related: Dangers in the deep: 10 scariest sea creatures But researchers have visited the habitat so many times and never seen the adult stage of that hypothetical larval jelly, she added. Another theory posited that jellyfish still in their larval stage (and thus microscopic) might float through the water and sting people. "We initially thought that there would maybe be some tentacle bits from other jellyfish" floating through the water, perhaps detached during a massive spawning event, as can happen, Ames said. ![]() None of the proposed explanations held up to scrutiny. ![]() Sea lice are parasites that prey on fish, but the term serves as a colloquial "catchall" for anything that causes water to sting, Ames said. Those familiar with stinging water may have heard of so-called sea lice, creatures often blamed for the painful sensation associated with upside-down jellies. ![]()
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