In Brief
Fang blennies are one of only two species of fish that deliver venom through a bite. The fish use this as a form of protection from would-be predators. The venom contains opioids which dull the pain of the bite.

Unique Venom

Venomous fish are not unheard of in nature. Reef stonefish and lionfish have venomous spines that can release toxins into potential prey or in defense. However, it is uncommon to find fish that deliver their venom by bite, like the tiny, brightly colored tropical fish known as fang blennies. Even more novel, the venom of this tropical fish contains opioid hormones. That’s right, there’s a fish that is biting heroin-like venom into its unlucky victims.

The fang blennies don’t use their bite to capture prey, it’s used more for defense. Researchers think that the bite makes the blood pressure of their predators drop, making it easier for them to escape. “If you had such a big crash in blood pressure, you would immediately feel faint and dizzy,” said Nicholas Casewell, an author of the study. “We don’t know that fish get faint or dizzy, but it’s extremely likely such a large drop would impact coordination and swimming ability.”

The fish’s venom has previously been studied by zoologist George Losey. Losey not only tested the fang blenny venom on mice but he also forced the fish to bite him. It took nearly 40 years to discover what is in that venom. The study has been published in Current Biology.

Photo credit: Brian Gratwicke/Flickr
Photo Credit: Brian Gratwicke/Flickr

Mimicry is the Sincerest Form of Flattery

Only about 30 percent of fang blenny species are venomous, but this doesn’t stop predators from avoiding them altogether. Some non-venomous species mimic the colors and patterns of venomous species to trick predators into leaving them alone. Even more, species of fish that aren’t blennies whatsoever have been observed doing the same. Both blenny and other copycat species will imitate the bright coloring and swim patterns of the venomous fish to keep predators at bay.

Fish venom is a particularly understudied aspect of biology. Other venoms, such as those from snakes, scorpions, and spiders, are heavily researched to develop new medications and treatments. Perhaps the great variety of venomous sea creatures could open up a whole new world of possibilities in research.