Stephanie Edwards is the Engagement Specialist at Discover Magazine, who manages all social media platforms and writes digital articles that focus on archaeology, the environment, and public health.
There are many examples of members of the animal kingdom stealing from one another, whether it be prey, shelter, or nutrients. A fish species — known as the golden sweeper — has added a new, unexpected item to the list: the ability to glow.
New research, published in Scientific Reports, confirmed that the golden sweeper fish doesn’t produce its own bioluminescence at all, but steals the ability from other organisms.
This finding is the clearest evidence yet of a rare biological strategy called “kleptoproteinism,” and it could reshape how scientists think about how life works at the genetic level.
A golden sweeper fish emits light using stolen bioluminescent proteins.
(Image Credit: Government Park (Ocean Expo Park)/Okinawa Churaumi Aquarium)
What Is Kleptoproteinism?
In most living organisms, biological functions are tightly controlled by genes. If an animal glows, it’s because its DNA encodes the machinery to make that happen. This principle forms one of the backbones of modern biology.
But the golden sweeper fish (Parapriacanthus ransonneti) breaks that form.
Instead of producing its own light-generating enzyme — known as luciferase — the fish acquires it directly from its prey. Specifically, it feeds on tiny bioluminescent crustaceans called ostracods or “sea fireflies,” and repurposes their glowing proteins for its own use.
This phenomenon falls under a broader category known as kleptobiology, where organisms borrow useful biological components from others. But kleptoproteinism, where organisms steal and use fully functional proteins, is especially rare.
How Scientists Identified Kleptoproteinism in Fish
For years, the research team wasn’t sure whether the fish truly lacked the gene for luciferase or had somehow acquired it through horizontal gene transfer. To settle the question, scientists conducted a high-resolution genome sequencing of P. ransonetti with the goal of either finding the gene responsible for producing luciferase or confirming that it wasn’t there at all.
After analyzing the fish’s genome, researchers found no trace of luciferase genes and no evidence that genetic material had been transferred from its prey. In other words, the fish has no internal design for making light.
“These results provide compelling and conclusive evidence that this fish does not possess the genetic blueprint for bioluminescence,” said Manabu Bessho-Uehara, associate professor at Tohoku University, in a press release. “Instead, it relies entirely on proteins obtained from its prey, representing a truly unique form of biological adaptation.”
To eliminate the change for contamination, the team used live specimens originally collected by Okinawan fishermen in July 2021. For 15 months, the fish were fed non-luminous food, ensuring that any detected genetic material came solely from the fish itself.
How This Discovery Could Shape the Future of Medicine
This discovery opens new questions about how the fish preserves and uses foreign proteins without breaking them down.
In most animals, ingested proteins are rapidly digested into amino acids. But P. ransonneti appears to protect these proteins, transport them intact, and deploy them for biological use — a mechanism that could have major real-world applications.
If researchers can figure out how these proteins survive digestion and remain active, it could inform new strategies for drug delivery, one of the long-standing challenges of modern medicine.
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Stephanie Edwards is the Engagement Specialist at Discover Magazine, who manages all social media platforms and writes digital articles that focus on archaeology, the environment, and public health.View Full Profile
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