Why is seawater so stingy? Jellyfish snot!

Bottom dwelling upside down jellyfish cause stinging water from toxic mucus.
Bottom dwelling upside down jellyfish cause stinging water from toxic mucus.

Florida’s warm coastal waters can sometimes burn swimmers like “stinging water.” But why?

Even without brushing against jellyfish, swimmers have complained of irritating stings which can be from sea lice, anemones, severed jellyfish tentacles and other stinging marine animals.

But scientists discovered mucus from upside-down floating jellyfish can lead to irritating stings even without contact.

The mucus is filled with toxins from a type of jellyfish called Cassiopea that inhabits the muddy bottom of Florida’s inshore bays and shallow lagoons.

If disturbed the jellyfish may pulsate their bells and rise in the water, soon flopping back onto the seabed.

When agitated or feeding, a cloud of mucus is released packing gyrating balls of stinging cells called cassiosomes. The toxin is strong enough to kill tiny sea shrimp and cause a mild sting on human skin.

National Oceanic and Atmospheric Administration zoologist Allen Collins and colleagues worked together to find the cause and published the results in the Feb. 13 issue of the journal Nature Communications Biology.

Collins said the team’s discovery was particularly exciting because Cassiopea jellyfish have been recognized for more than 200 years, but cassiosomes have remained unknown until now.

“They’re not the most venomous critters, but there is a human health impact," according to Collins’ article.

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