The fearless coral reef fish known as the fang blenny might only grow to several inches long, but it packs a toothy, venomous bite. New research into the fang blenny family tree reveals how their fangs and venom evolved – and hints at how these fish disable potential predators with a heroin-like, pain-killing venom.
There are five genera of fang blennies, one of which (Meiacanthus) is venomous. These beautiful and territorial fish are found on Australia’s Great Barrier Reef and other tropical locations. In fighting for space and defending themselves from larger predators, their secret weapons are two large, grooved teeth on the lower jaw linked to venom glands.
Bryan Fry of the University of Queensland and collaborators reconstructed the evolutionary relationship of fang blenny species. They analyzed their fangs and, if present, their venom delivery system.
All fang blennies have grooved fangs on their lower jaw, but only Meiacanthus species have venom glands and grooves for the venom to travel to the fangs. Fry and his colleagues determined that, unlike in venomous snakes, where venom evolved before the fangs that could deliver the weapon, fang blennies evolved fangs first and venom later.
“The ancestral fish was an animal that used the fangs to scoop out flesh from larger fish, much like how the fang blenny species Plagiotremus rhinorhynchos (the bluestriped fangblenny) mimics a cleaner wrasse in order to feed on larger fish thinking they’re going to get a cleaning,” says Fry.
“A total asshole move, of course, since that bigger fish is going to take this out on the next innocent cleaner wrasse it encounters!”
In Meiacanthus species, evolution co-opted these fangs from their ancestral purpose for the delivery of venom to fight off potential predators.
Fry and his colleagues analyzed Meiacanthus fang blenny venom and found it to be multifunctional, containing a number of toxic components. The venom reduces blood pressure and also acts on opioid receptors, behaving like heroin or morphine to inhibit pain rather than cause it.
“Any opioid is going to slow down the body and cause dizziness, aspects that are going to help a fang blenny escape a predator or defeat a competitor,” says Fry.
Fry says that this discovery is an excellent example of why we must urgently protect all of nature; it is impossible to predict where the next wonder drug will come from.
“The Great Barrier Reef is currently dying due to the effects of climate change and the Australian government has been shockingly inactive to responding to this threat,” he says.
“Instead, it has just approved the largest coal mine in Australia’s history, an action that will contribute to climate change and thus further threaten biodiversity-based medical research.
“If we lose the Great Barrier Reef, we will lose animals like the fang blenny and its unique venom.”
Casewell, N. R. et al. (2017). The Evolution of Fangs, Venom and Mimicry Systems in Blenny Fishes. Current Biology 27:1-8. doi: 10.1016/j.cub.2017.02.067.