<p>Marine invertebrates called pyrsomes are appearing in record numbers in areas where they had rarely been seen before.</p>

Marine invertebrates called pyrsomes are appearing in record numbers in areas where they had rarely been seen before.

Photograph by Steve Morey

Bizarre, Glowing Sea Creatures Bloom in the Pacific

Tropical, tube-shaped animals called pyrosomes, known as "fire bodies," appear by the millions off the Pacific Northwest and Alaska. No one knows why.

After three years of unprecedented warm water along the U.S. West Coast, sea temperatures in 2017 had finally cooled. Fat shrimplike krill had returned and again were providing rich meals for salmon. Sea lions and other marine mammals were no longer washing ashore shriveled and starving. Things appeared to be getting back to normal.

Then they showed up.

Beginning this spring, millions of bizarre primitive-seeming jellyfish-like bioluminescent sea creatures—some more than two feet long—started gumming up research nets, glomming onto fishing hooks, and cascading onto beaches along the West Coast. These stubbly gelatinous animals called pyrosomes (each is technically a colony of other multi-celled animals called zooids) are cone-shaped tunicates normally found in the tropics, but they

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