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Bioluminescent helmet jellyfish glowing blue against a black deep-sea background

Helmet jelly

Periphylla periphylla

Not on exhibit
Animal type
Invertebrates
Ecosystem
Deep sea
Relatives
Other jellies; Order: Coronatae
Diet
Zooplankton
Range
Worldwide (except for Arctic Ocean) from the surface to 13,000 ft. (4,000 m)
Size
Up to 10 inches (25 centimeters) diameter

Meet the helmet jelly

Flashing lights mean “back off!” At the hint of danger, a bright-blue strobe washes over the helmet jelly’s bell. In pitch-black water, these flashes may spook predators so the jelly can swim to safety.

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