‘Mysterious’ pickle-shaped sea critter that glows is seen on Oregon beach. What is it?

A “mysterious” sea creature that can glow has been spotted on an Oregon beach.

“I spy with my little eye a wee little pyrosome,” Seaside Aquarium wrote in a Facebook post about a handful of the critters spotted on Seaside Beach on Feb. 9.

The creatures graced the coast of Oregon “en masse” in previous years, according to the aquarium.

“Will we see them in the numbers we saw in 2016-2017?” the aquarium wrote. “Only time will tell.”

‘Invasion of the pyrosomes’

There was an explosion of pyrosomes off the Northwest Coast in 2017, the National Oceanic and Atmospheric Administration said in a June 2017 news release.

“Call it the invasion of the pyrosomes,” the agency said.

Two years prior, NOAA said the creatures “were rarely if ever seen off the Northwest.”

But in spring of 2017, NOAA said they appeared “to be everywhere off the Oregon Coast.” They clogged “fishing gear by the thousands.”

“At first we didn’t know what to make of these odd creatures coming up in our nets, but as we headed north and further offshore, we started to get more and more,” Hilarie Sorensen, a University of Oregon graduate student, said in the release.

Months later, the creatures made their way to Alaska, “a never-before-seen phenomenon,” NOAA said in an October 2017 news release.

“This is our first encounter with pyrosomes in the Gulf,” Wayne Palsson with Alaska Fisheries Science Center said in the release.

What are they?

The animals, “often called sea pickles or sea squirts,” are usually found in tropical waters, the aquarium said.

However, the aquarium said “stormy ocean conditions” can bring the “mysterious creatures as far north as Alaska.”

Of the pyrosome species, Pyrosoma atlanticum is the most common one found on Oregon shores, the aquarium said. This species is a “rigid, bumpy, pinkish-gray tube about the size of a finger” and can reach up to 2 feet in length.

Other species found in the world, though, range in size, with some measuring just a few centimeters and others reaching 30 feet in length, according to the aquarium.

The critters are “known as a colonial tunicate,” meaning they are made up of thousands of smaller organisms, the aquarium said.

The “thousands of cloned zooids” make the “cylinder-shaped, tube-like body,” the aquarium said.

The organisms are connected by tissue that allow “communication and coordinated behavior,” according to the aquarium.

To feed, the animal “move their cilia (hair-like structures),” drawing in water and filter-feeding on plankton, the aquarium said.

Once “plankton is caught on mucus,” the zooids throw out the water which in turn propels their bodies through the sea, the aquarium said.

The creature can travel 2,500 feet, or nearly half a mile, in a day, according to the aquarium.

The critter’s scientific name, pyrosoma, which translates to “firebody” in Greek, is an homage to their bioluminescence, or ability to create light,

Scientists theorize the creatures use this glowing trait “to attract plankton to eat,” the aquarium said.

Pyrosomes thrive where “ocean conditions promote plankton blooms,” according to the aquarium.

“Bony fish, dolphins and whales” are all known predators of pyrosomes, the aquarium said.

The slow-moving creature is harmless to humans, according to the University of Oregon.

“They have been called ‘unicorns of the sea’ because they are so strange and appeared out of, it seems, nowhere,” the university said.

Seaside is about 80 miles northwest of Portland.