Fangblenny bite delivers opiod-containing venom that drops blood pressure and ignites inflammation in victims

If a predator fish tries to swallow a tiny fangblenny, the hunter receives such a compelling dose of venom from its prospective lunch that the larger fish quivers and opens its mouth, letting the fangblenny escape unharmed. When Nicholas R. Casewell of the Liverpool School of Tropical Medicine, Bryan G. Fry of the University of Queensland, and colleagues took a close look at venomous fangblennies of the Meiacanthus genus, they discovered that the fish’s propensity to deliver toxic deterrents has some peculiar attributes (Curr. Biol. 2017, DOI: 10.1016/j.cub.2017.02.067). For example, many fish that use venom for defense rely on sharp spines to deliver their cargo; the fangblenny uses fangs. Furthermore, venomous fangblennies evolved their fangs before they evolved the biochemical ability to produce venom. Initially, the fish may have used the fangs to scoop out the flesh of competitors or to give predators a sharp poke. The team also discovered that fangblenny venom contains potent phospholipases that chop up membranes to cause inflammation. These enzymes are common constituents of bee, scorpion, and snake venom, and the activity of fangblenny phospholipases is on par with that of pit viper snake phospholipases. The venom also contains neuropeptides and proenkephalin, a peptide that targets opioid receptors. These latter two components make a victim’s blood pressure plummet and may interfere with coordination and swimming—outcomes that would certainly facilitate the fangblenny’s escape.