Scientists find glow-in-the-dark protein in your sushi

A freshwater eel popular among sushi aficionados holds the first fluorescent protein found to have naturally occurred in a vertebrate.

Toshiyuki Aizawa/Reuters
An owner of a Japanese eel restaurant shows live eels before preparing them for cooking in Tokyo's business district, in 2001. Scientists have recently discovered a fluorescent protein in unagi, a genus of endangered eels that are regarded as a delicacy.

A fluorescent protein – the first ever found naturally occurring in a vertebrate – has been spotted in a freshwater eel that is common on sushi menus but becoming scarce in the wild.

Anguilla japonica, also known as unagi, is born in the sea. As eggs and larvae they are carried by ocean currents to rivers, lakes, and estuaries in Japan, China, Taiwan, Korea, and Vietnam, where they spend their lives until returning to the sea to spawn.
The carnivorous fish also possess a glow-in-the-dark protein in their muscles, as scientists at Japan's RIKEN Brain Science Institute have found. In a study published in the scientific journal Cell, researchers describe what they've named UnaG, the first fluorescent protein found to have come from a vertebrate. The researchers believe that the glowing protein aids in the species' migration.

UnaG is a fatty-acid-binding protein found in the unagi's muscle fibers. The researchers were surprised to find that it glowed only when activated by a chemical called bilirubin, a breakdown product of molecules found in blood. The scientists also identified the protein in the American and European species of Anguilla.

Bioluminescence, the production and emission of light by a living organism, can be found in many species of microbes, plants, and animals, including many other marine vertebrates. Some species, such as the anglerfish, use glowing bacteria to cast light underwater. Other species, such as the lanternfish, emit light through chemical reactions. Until this discovery, it was unknown how the eels emitted green light. Fluorescent proteins have been found naturally occurring only in some species of jellyfish.

The jellyfish genes that code proteins for bioluminescence have been successfully introduced in mammals, however. In 1998, a performance artist paired with a geneticist to produce Alba, a rabbit with glowing green fur. Scientists in Taiwan have also used gelatinous sea creatures' fluorescent genes to create glowing pigs.

Unagi for its part, remains a popular delicacy. But it is being dined to extinction. In February, the Japanese government declared Anguilla japonica, "likely to be extinct in the wild in the near future" and added it to its endangered species list. In a RIKEN press release, the researchers note that they hope this discovery will aid in conservation efforts.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to

QR Code to Scientists find glow-in-the-dark protein in your sushi
Read this article in
QR Code to Subscription page
Start your subscription today