Scientists have just uncovered an astonishing secret about a little fish that resides in the Great Barrier Reef in the Pacific Ocean, and it’s a discovery that could lead to breakthroughs in medicine. The tiny fish, known as the fang blenny, injects predators and competitors with a substance that is very much like heroin, disabling the foe.

The venom acts a lot like modern opioids, which are used as painkillers in human medicine. It’s a big find because it’s possible that it could be synthesized and used as a pain-killing peptide, but a lot of studies will need to be performed before it could be used in humans.

But if it could be turned into a painkiller that serves as an alternative to opioids, that would be a huge boon to the medical community because of all the negatives associated with opioids, such as addiction and overdose risks.

Fang blennies are often found in aquariums in people’s homes. They are bottom-feeders that like to live off reefs, and they are under threat due to climate change. This discovery is a good example of why protecting the reefs and the Earth’s species in general is good not just for the natural world but for humans.

“For the fang blenny venom to be painless in mice was quite a surprise,” says study co-author Bryan Fry of University of Queensland. “Fish with venomous dorsal spines produce immediate and blinding pain. The most pain I’ve ever been in other than the time I broke my back was from a stingray envenomation. ‘Sting’ray sounds so benign. They don’t sting. They are pure hell.”

“Predatory fish will not eat those fishes because they think they are venomous and going to cause them harm, but this protection provided also allows some of these mimics to get very close to unsuspecting fish to feed on them, by picking on their scales as a micropredator,” says study co-author Nicholas Casewell of the Liverpool School of Tropical Medicine. “All of this mimicry, all of these interactions at the community level, ultimately are stimulated by the venom system that some of these fish have.”