Rare Footage Of Bizarre Cnidarian Reminds Us We've Just Got To Deal With What's In The Sea

The sea pen is actually a colony of animals, not one.


Rachael Funnell

Social Editor and Staff Writer

clockJul 29 2022, 12:08 UTC
sea pen
Just the ocean being totally normal. Image courtesy of the Ocean Exploration Trust, NOAA & Oregon State University/Thurber

A three-week expedition to a previously unexplored stretch of the Pacific Remote Islands Marine National Monument (PRIMNM) recently turned up a remarkable find as researchers stumbled across a Pacific Ocean sea pen for the first time. The colonial cnidarian isn’t actually an animal, but a colony of animals living together in what looks like a Demogorgon apartment complex.

“At 2,994 meters [9,820 feet] on a never-before-surveyed seamount north of Johnston Atoll, the team spotted an animal for the very first time in the Pacific Ocean,” said Ocean Exploration Trust, NOAA, Nautilus Live in a statement emailed to IFLScience.


“The sea pen, a colonial cnidarian, had a single large feeding polyp with pinnate (barbed) tentacles stretching over 40 centimeters [16 inches] from its 2-meter-long [6.5-foot] stalk.”

Cruising on the remotely operated vehicles (ROV) Atalanta and Hercules, the researchers piloting got the pleasure of witnessing Solumbellula monocephalus in the flesh, an observation that until now had only been made in the North and South Atlantic and Indian Oceans. Whether the cnidarian represents the first of the species found in the Pacific, or a new species altogether, remains to be determined, but it sure makes for one hell of a video.

“With the ROVʻs cameras, the team had some beautiful close-ups of this coral relative on an unnamed underwater mountain sedimented saddle,” said Nautilus Live. “We were astounded with a detailed view of its stinging feeding tentacles that capture marine snow and food particles drifting by.”


The researchers were treated to not just one but two individuals on their Pacific jaunt, indicating that there exists a population of these alien creatures which falls under the protection of the Johnston Unit of PRIMNM.

The sea mounts at this site are estimated to be between 70 and 100 million years old, and through their explorations, the team at Nautilus Live hope to get a clearer picture of the biodiversity within the region and learn more about how it was formed.

Hungry for more ocean oddities? You can follow the Nautilus Live Ocean Exploration Trust's expeditions via live streaming at

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