A new study from Tohoku University in Japan found that Parapriacanthus ransonneti, a small species of goldeneye fish living in the Pacific Ocean, obtains its own bioluminescent ability by "stealing" luminescent molecules from its prey. It is considered to be the only known example of an animal that "imports" luminescent proteins in this way.
Researchers found through high-precision whole-genome sequencing that this small fish, about 7 centimeters in length, lacks the gene for the key enzyme responsible for bioluminescence, luciferase, and there is no evidence of acquiring the gene from other species through "horizontal gene transfer." Normally, bioluminescence requires the organism itself to carry and express the relevant genes, but the goldeneye seabream has no genetic blueprint for synthesizing this light-emitting enzyme.
On the contrary, the team confirmed that this fish directly obtains the luciferase protein that has been synthesized in the opponent's body by preying on a kind of prey called "sea firefly" (luminous plankton belonging to the crustacean and ostracods), and "transports" it to its own light-emitting organ for use. The researchers wrote in the paper that this approach means that the goldeye bream cannot produce luciferase itself, but achieves light by "hoarding and utilizing the luciferase protein of prey", a phenomenon known as "kleptoproteinism."
This mechanism is similar to a kind of "stealing" at the molecular level. When the golden-eyed seabream preys on luminous ostracods, it does not obtain the opponent's DNA or genes, but directly grabs the functional proteins that have been produced by the opponent and redeploys them in its own tissues. This pattern is extremely rare in nature and is the only vertebrate case that has been clearly reported to gain function by "stealing prey proteins."
Research points out that this strategy has obvious advantages in energy economics. Maintaining a set of genes and metabolic pathways that can independently produce luminescent enzymes and related chemical molecules will impose a considerable energy burden on organisms. The golden-eyed seabream uses "outsourced production" to leave the expensive biochemical synthesis process to its prey such as sea fireflies. It is only responsible for catching and recycling these ready-made molecular "resources", thereby saving energy while gaining the ability to emit light.
Even more surprising is that this bioluminescence is not used to attract mates or trap prey, but is used for camouflage and stealth. The research team explained that in dim moonlit waters, when predators look up at a school of fish from below, they can identify the target through the silhouette of the fish in the water. But once the goldeye snapper uses the "stolen" luminescent proteins in its body to light up its abdomen and other light-emitting organs, it can offset its own shadow under the background light of the water body and visually integrate with the surrounding environment. This strategy is called "counterillumination camouflage."
In the captured images, the researchers showed the blue light emitting from the ventral surface of the goldeneye snapper, and pointed out that these enzymes and chemical molecules used for bioluminescence are not biosynthesized by the fish itself, but are obtained from prey through eating and stored in the body. This "invisibility cloak"-style luminous camouflage is one of the most sophisticated concealment methods known in nature, greatly improving the ability of fish to avoid predators in the ocean.
However, this "outsourced luminescence" strategy also has a prerequisite, that is, the golden-eyed sea bream must be in an environment with enough "sea firefly" prey for a long time, so that it can continuously "replenish" the internal luminescence system. The research team pointed out that every time you eat luminescent ostracods, it is equivalent to "fueling" the luminescent protein in the body. The luminous intensity does not remain constant, but is constantly updated as the protein is consumed and eaten again.
The authors of the paper emphasize that their findings indicate that organisms can acquire new functions directly by "robbing" prey proteins during evolution without relying on horizontal gene transfer. At present, the specific protein "hijacking" and transport mechanisms have not been fully elucidated, but the whole-genome data of the goldeye seabream provides a basic platform for further research on the evolution and molecular mechanism of the "stealing protein luminescence" system.
This research has been published in Scientific Reports, and a related press release was officially released by Tohoku University in Japan. Scientists believe that this discovery not only refreshes people's traditional understanding of bioluminescence and gene function distribution, but also provides a unique perspective for understanding how organisms survive and adapt in energy-limited environments through extreme "resource conservation" strategies.