Thousands of creatures resembling penises have washed up on a beach in California.
The pulsating creatures are fat innkeeper worms, or Urechis caupo.
Although they are a type of worm, they are widely referred to as the "penis fish".
The worms bury themselves deep beneath the sand, but recent storms have uprooted them and Drakes Beach, about 50 miles north of San Francisco, has been covered in the creatures.
"Yes, the physical design of the fat innkeeper worm has some explaining to do. But the fat innkeeper is perfectly shaped for a life spent underground," wrote biologist Ivan Parr.
There is fossil evidence of the creatures dating back 300 million years and some live for up to 25 years, he added.
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SHOOK 😳 Thousands of these marine worms—called fat innkeeper worms, or “penis fish”—were found on Drake’s Beach last week! These phallic organisms are quite common along the West coast of North America, but they spend their whole lives in U-shaped burrows under the sand, so few beachgoers are aware of their existence. ⛈🌊 A recent storm in Northern California brought strong waves that washed away several feet of sand from the intertidal zone, leaving all these fat innkeeper worms exposed on the surface. 🏖 Next time you go to the beach, just think about the hundreds of 10-inch, pink sausages wiggling around just a few feet under the sand. 🙃 . . Get the full story in our new #AsktheNaturalist with @california_natural_history via link in bio! (📸: Beach photo courtesy David Ford; Worm photo by Kate Montana via iNaturalist)
Within a beach, the creatures will dig a U-shaped burrows extending several feet long.
Their more polite nickname - innkeeper worm - comes from this subterranean lifestyle and the tunnels they create for other animals as they burrow underground.
Several other species, including fish, sharks, and otters feast on the penis fish.
And it's considered food for humans as well. Urechis unicinctus, the species found in East Asia, is a delicacy in countries including South Korea.