Researchers have discovered a fish venom that contains opioid properties, which could help in the development of new pain-killing drugs.

The fierce-looking fang blenny, also known as the poison-fang blenny or the sabre-tooth blenny, fends off predators and competitors by injecting them with a heroin-like substance that impairs them rather than kills them.

"The venom causes the bitten fish to become slower in movement and dizzy by acting on their opioid receptors," said Bryan Fry, who led the study published Tuesday in the science journal Current Biology. Although used for defence, the venom "inhibits pain rather than causing it."

It is impossible to predict where the next wonder drug will come from. - Bryan Fry, associate professor, University of Queensland

It's not the first time animal poison has been found to have analgesic properties: Ziconotide which was derived from cone snails, is used to treat chronic pain. But it's the first time scientists have identified opioid peptides in fish venom, Fry said.

The venom is "chemically unique," which drives home the importance of biodiversity, said Fry of the University of

Queensland.

"This discovery is an excellent example as to why we must urgently protect all of nature," Fry told CBC News. "It is impossible to predict where the next wonder drug will come from."

Existence 'threatened'

But there's no wonder drug just yet. Scientists still have to figure out how to synthesize and use the pain-killing peptides.

"The next step is now to study these peptides further and continue sequencing them," Fry said. "This may reveal versions that are longer lasting, more potent or with less side effects."

But the discovery offers hope for the development of a next-generation painkiller at a time when opioid addiction has become a pressing public health issue.

Fang blennies are a popular aquarium fish, usually bottom-feeders that are found in reefs like Australia's Great Barrier Reef. As those formations degrade due to climate change and other factors, the world risks losing an important potential trove of discovery.

"These fish are found on the Great Barrier Reef, so their existence is as threatened as that of the reef itself," Fry said. "Destroying the reef is no different than popping a nuclear bomb on top of an oil field. It is the wilful destruction of a vast economic resource."