Published: Wed, April 05, 2017
Science | By Boyd Webster

These Tropical Fish Have Opioids in Their Fangs

These Tropical Fish Have Opioids in Their Fangs

After analyzing the venom, specialists determined that it contains three toxins, namely an opioid as risky as heroin, a molecule used in neuron signaling and an enzyme. The researchers dealt with the problem by taking the fishes out of their tanks and dangling cotton swabs in front of the blennies until they bit it.

The biggest impact of the new research is how it shines a spotlight on fish venom in general.

Fish venom has been understudied for most of the time.

The skeleton of a fang blenny, showing the two sharp teeth on the lower jaw. Fry said that the pain he felt "from a stingray envenomation", was like "pure hell".

Fang blennies, even if they are small, feature a strong pair of canines, having a venomous bite. "In this case, the side-effect is what's being used by the blenny", he says.

These morphine-like compounds cause a sudden drop in blood pressure, apparently disorientating a predator and letting the blenny escape. Because the researchers used mice for the pain test, they can't rule out the possibility that the venom does cause pain when injected into other fish.

"While the feeling of pain is not produced, opioids can produce sensations of extremely unpleasant nausea and dizziness". But until now, no one was sure how the venom actually worked. The grouper, on the other hand, was so scarred by the experience that it developed an aversion to this particular genus of fish.

"To put that into human terms, opioid peptides would be the last thing an elite Olympic swimmer would use as performance-enhancing substances", says co-author and University of Queensland researcher Bryan Fry. Animals like snakes, scorpions and spiders are generally used for this kind of research, but with so many venomous fish out there, we could find some useful chemicals in them, too. It's a very unusual evolutionary line. "They fearlessly take on potential predators while also intensively fighting for space with similar sized fish". Casewell added that it appears as if evolution favored the little fang fish with large teeth and later by filling them with venom.

Fry believes that the fang blennies use their venom to slow down their predators when they try to escape.

Scientists have discovered a chemically unique venom in small tropical fish known as fang blennies.

"All of this mimicry, all of these interactions at the community level, ultimately are stimulated by the venom system that some of these fish have".

Findings about blennies and painkillers bolster the need to protect the Great Barrier Reef and other fragile ecosystems. The Great Barrier Reef is in danger, and destroying this habitat would mean destroying the chance to use the miraculous venom to develop new and effective drugs.

The team started their study with "no grand hypothesis, just basic wonderment" says Fry, but given the results they plan to continue the study by analyzing the composition of venoms from different blenny species.

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