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Nature

Penis Fish

What is penis fish?

· Emily Grant

Key facts

Scientific name Urechis unicinctus[2]
Common name fat innkeeper worm[2]
Type marine spoon worm[2]
Alternative referent candiru, a parasitic catfish of the genus Vandellia[1]
Korean name Gaebul[2]

Penis fish is a common name for more than one organism, but it most often refers to *Urechis unicinctus*, a marine spoon worm also called the fat innkeeper worm. The term can also refer to the candiru, a parasitic catfish.

Context

The term "penis fish" is a common name that applies to different organisms depending on the source. In most reports, it refers to *Urechis unicinctus*, a marine spoon worm also called the fat innkeeper worm, which lives in East Asia and is known as Gaebul in Korea [2]. The BBC described California beach strandings of these worms as "a type of worm," not fish [3]. The term is also used for the candiru, a parasitic catfish of the genus *Vandellia*, which has been alleged to enter the human urethra [1]. Because the name covers both a worm and a catfish, the intended meaning depends on the context [1].

Documented claims

  • Urechis unicinctus is a marine spoon worm, not a fish. [2]
  • The candiru is alleged to be able to enter the human urethra. [1]

Questions and answers

What does a candiru fish do?

The candiru is a parasitic catfish that has been alleged to enter the human urethra [1].

Is the urethra fish a myth?

The candiru is described as "alleged to be able to enter the human urethra," meaning the claim is not confirmed [1].

Are penis fish actually fish?

No. *Urechis unicinctus* is a marine spoon worm, not a fish [2].

Sources

  1. Is There Really a 'Penis Fish' That Swims up the Urethra? — healthline.com (retrieved August 3, 2026)
  2. 'Penis fish' wash up on a beach in California — bbc.com (retrieved August 3, 2026)
  3. Gaebul: The fat innkeeper worm (AKA the penis fish) - bburi kitchen — bburikitchen.com (retrieved August 3, 2026)

Sources last checked August 3, 2026. · More in Nature