These Tiny Fish Use Their Venom to Kill ... Pain

The striped fang blenny, native to the western Pacific, is one of several venomous blenny species. (Photo: apathosaurus/Shutterstock)

Fang blennies are cute little coral-reef fish from the Indian and Pacific oceans, but despite their unimposing appearance, they're no pushovers. As their name suggests, they have fangs — pretty serious fangs. They're also venomous, and as a new study has found, fang blenny venom is unlike any other venom known to science.

And while it's used as a weapon in the wild, this bizzare venom could be uniquely useful to humans, researchers report in the journal Current Biology.

A wide range of animals have evolved a wide range of venoms over time, chemicals that tend to be painful and are often used to disable prey. Fang blennies, however, don't use venom to hunt, instead feeding mainly on plankton. And when they do use their venom, it's not only painless — it apparently acts as a painkiller.

"The fish injects other fish with opioid peptides that act like heroin or morphine, inhibiting pain rather than causing it," says University of Queensland researcher Bryan Fry, one of 23 co-authors who worked on the new study, in a statement. "Its venom is chemically unique. The venom causes the bitten fish to become slower in movement and dizzy by acting on their opioid receptors.

"To put that into human terms," Fry continues, "opioid peptides would be the last thing an elite Olympic swimmer would use as performance-enhancing substances. They would be more likely to drown than win gold."

Venomous, but not vicious

forktail blennies, Meiacanthus atrodorsalis
Forktail blennies swim among corals off the coast of Malaysia. (Photo: Bernard Dupont/Flickr)

Rather than helping fang blennies catch food, this venom may have evolved to help them avoid becoming food, the study's authors say. Animals that receive the venom experience a brief but potentially debilitating drop in blood pressure, which could slow them down enough to let the blenny swim for safety.

This "secret weapon," Fry explains, lets tiny blennies be surprisingly bold.

"Fang blennies are the most interesting fish I've ever studied and have one of the most intriguing venoms of them all," he says. "These fish are fascinating in their behavior. They fearlessly take on potential predators while also intensively fighting for space with similar sized fish. Their secret weapons are two large grooved teeth on the lower jaw that are linked to venom glands."

Science has learned to harness the power of many venoms for human benefit in recent years — snake venom can help with heart attacks and blood clots, for example, while spider venom may stop brain damage from a stroke. And despite the oddity of blenny venom, Fry and his colleagues say further study of its chemistry could help researchers develop new kind of painkillers for people.

A blenny saved is a blenny earned

blackline fang blenny, Meiacanthus nigrolineatus
A blackline fang blenny rests in a tube sponge in the Red Sea. (Photo: Rich Carey/Shutterstock)

Fang blennies, grouped into the genus Meiacanthus, are popular as ornamental tropical aquarium fish. In the wild, however, many depend on increasingly fragile ecosystems — coral reefs — whose troubles are too big to be solved by venom. These habitats face mounting pressure from human-related threats like ship collisions, coastal pollution and especially climate change, both due to ocean acidification and rising water temperatures, which can spur coral bleaching.

That includes the Great Barrier Reef, as Fry points out, a crown jewel of coral ecosystems that has suffered historic levels of bleaching lately. We already know many reasons why saving coral reefs is in humanity's own best interest, and as the fang blenny illustrates, we may still have only scratched the surface.

"This study is an excellent example of why we need to protect nature," Fry says. "If we lose the Great Barrier Reef, we will lose animals like the fang blenny and its unique venom that could be the source of the next blockbuster pain-killing drug."