Tiny Fish Foils Predators By Injecting Them With Opioid Venom

The tiny fish Meiacanthus nigrolineatus, also known as the fanged blenny fish, doesn't look like much, but it has a secret weapon to keep predators at bay: venom. This venom is used to stop predators in their tracks, causing their blood pressure to drop and their ability to eat the blenny to diminish. While most fang-based venom causes extreme pain in the victim, the blenny fish's venom is different because it contains, among other things, an opioid peptide.

According to a newly published study in Cell Biology, the fanged blenny fish causes low blood pressure in other fish it bites, and that low blood pressure likely causes the fish to become disoriented and unable to take off after the small fish. Whether the venom causes pain to the predator fish is unclear, but researchers found that it doesn't cause pain when injected into lab mice.

After going to great lengths to extract some of the venom from the small fish, researchers analyzed it and discovered that it contains the same kind of neuropeptide found in cone snail venom, as well as an opioid peptide and a type of lipase not unlike the kind found in scorpions.

Perhaps more surprising is another discovery — the likelihood that this version of the blenny fish evolved to have fangs before it evolved to have venom, representing a sort of accommodation by nature to take advantage of an already advantageous feature in the fish species. While the researchers don't say whether this venom could ever have any practical applications, other aquatic critters could, including the the Crown Cone snail with its non-opioid painkiller venom.

SOURCE: Phys.org