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Miniature creature — with a ‘chastity belt’ — discovered as new species in Colombia

In shallow murkey water in Colombia, a miniature creature appeared with a mysterious skin flap, researchers said.
In shallow murkey water in Colombia, a miniature creature appeared with a mysterious skin flap, researchers said. George Mendes Taliaferro Mattox, Astrid Acosta-Santos, Juan D. Bogotá-Gregory, Edwin Agudelo and Flávio C. T. Lima (2025)

Researchers and scientists who spend their careers searching for new species in every corner of the globe know their field better than anyone else.

But, what happens when they encounter something they’ve never seen before?

Researchers in the Amazon of Colombia made a mysterious discovery when taking a closer look at a fish collected from a forest stream, according to a study published Jan. 28 in the peer-reviewed journal Zootaxa.

It belonged to the “miniature fish genus Priocharax,” according to the study, and was just 0.7 inches long.

For the most part, it looked like the other fish in its family — translucent fins, opaque body, rounded snout and relatively large eyes.

There was one feature, however, that was different.

“The only thing intriguing with this particular species is the presence of the round skin flap,” study author George Mattox told McClatchy News in an email, “which we don’t have the slightest idea regarding its function.”

The miniature fish is less than one inch long, considered large compared to related species, researchers said.
The miniature fish is less than one inch long, considered large compared to related species, researchers said. Shared by George Mattox George Mendes Taliaferro Mattox, Astrid Acosta-Santos, Juan D. Bogotá-Gregory, Edwin Agudelo and Flávio C. T. Lima (2025)

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The “unusual” flap, located between the two bases of the pelvic fins, is a “loose skin flap” that is “attached only by its base and covering the urogenital pore,” a tube behind the anus that releases sperm or eggs, according to the study.

The flap is present in both males and females, but there doesn’t appear to be any muscles able to move the flap for the pore to function properly, researchers said.

“I had never seen such (a) structure in any other fish!” Mattox said. “It is almost like a chastity belt which is present in both males and females.”

The unique feature helped researchers identify the fish as a new species.

The flap covers the tube used to release sperm or eggs, researchers said.
The flap covers the tube used to release sperm or eggs, researchers said. Shared by George Mattox George Mendes Taliaferro Mattox, Astrid Acosta-Santos, Juan D. Bogotá-Gregory, Edwin Agudelo and Flávio C. T. Lima (2025)

“Regarding the skin flap, I think it is too soon to speculate on its function,” Mattox said. “The main importance of this structure so far is the fact that it is unique to this species, as far as I know. So it is a clear diagnostic feature (i.e., a characteristic unique that permits unequivocally to identify the species.)”

The fish is large compared to its smaller cousins, earning it the name Priocharax rex, meaning king, according to the study.

“P. rex is recorded from small, shallow (less than 3.2 feet deep), slow-flowing terra-firme dark water streams,” researchers said, and the streams are filled with silt, clay, leaf litter and logs.

Two other species of Priocharax were identified by Mattox and other researchers in September, McClatchy News reported. The species were unique because of their completely translucent bodies that reminded the researchers of ghosts. The fish were discovered in Brazil.

P. rex was collected from southern Colombia.

The research team includes Mattox, Astrid Acosta-Santos, Juan D. Bogotá-Gregory, Edwin Agudelo and Flávio C. T. Lima.

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This story was originally published January 29, 2025 at 11:42 AM with the headline "Miniature creature — with a ‘chastity belt’ — discovered as new species in Colombia."

Irene Wright
McClatchy DC
Irene Wright is a McClatchy Real-Time reporter. She earned a B.A. in ecology and an M.A. in health and medical journalism from the University of Georgia and is now based in Atlanta. Irene previously worked as a business reporter at The Dallas Morning News.
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