If you have ever gone swimming and felt a strange stinging sensation, it may have been caused by nearby jellyfish’s ‘mucus grenade’.
The recently-identified culprit is the upside-down jellyfish known as the Cassiopea. This inverted jellyfish inhabits tropical mangroves and lagoons around the world.
These jellyfish live an upside-down life because of the mutually-beneficial relationship they have with photosynthetic algal cells. These algal cells, or microscopic seaweeds, colonize what is typically considered the underside of a jellyfish. For these algal cells to receive enough sunlight to photosynthesize, the Cassiopea jellyfish must lay upside down. For this same reason, Cassiopea jellies are commonly found in shallow, clear water – where swimmers often hang out.
As it turns out, the unnerving stinging sensation many swimmers experience coincides with being near, but not touching, Cassioipea jellyfish. First, scientists discovered that Cassiopea jellyfish kept in aquariums released clouds of mucus when agitated or feeding. This got Cheryl Ames wondering if this same mucus was behind the stinging sensation.
Ames’ curiosity led her to employ sophisticated imaging methods to get a close-up look at the insides of these mucus balls. It turns out the mucus is covered in the same stinging cells found on jellyfish tentacles – nematocysts.
“This discovery was both a surprise and a long-awaited resolution to the mystery of stinging water,” said Cheryl Ames, Smithsonian . museum research associate and associate professor at Tohoku University. “We can now let swimmers know that stinging water is caused by upside-down jellyfish, despite their general reputation as a mild stinger.”
Interestingly, the mucus balls, dubbed ‘cassiosomes’, come equipped with propulsion cells that help aid in the mucus mass’s movement, and with a bundle of the symbiotic algae. It is not yet understood why these ‘mucus grenades’ have these extra features.
Nonetheless, the mystery of the stinging water has been solved.
