Venomous fish are almost always purely defensive, lionfish an exception

8 Jul 20163 Shares

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A new study into various forms of venomous fish has found that 95pc of them only strike out in defence, but a handful are a bit more aggressive than that.

Venom has evolved 18 distinct times in fresh and saltwater fish, with spiny-rayed fish the primary drivers of change.

That’s according to a new piece of research that catalogues up to 3,000 venomous fish, and found that 95pc use their lethal doses only in times of defence.

Venom fish

The likes of lionfish and one-jawed eels, though, actively use their venom to kill prey. That shows just how big an issue the influx of lionfish into the Mediterranean, discovered earlier this month, may become.

Rising sea temperatures and the widening and deepening of the Suez Canal has led to an invasion of the foreign predator, posing threats to both prey, as well as competition.

This is a close up of the venomous dorsal-fin spine in a lanternshark, via W. Leo Smith and Jennifer H. Stern

This is a close up of the venomous dorsal-fin spine in a lanternshark, via W. Leo Smith and Jennifer H. Stern

Forms of attack

“Invasive lionfish will orient themselves in a strange way and ram themselves at people,” said William Leo Smith, lead author on the paper. “One-jawed eels have lost the upper jaw, but with the lower one they slam prey up into a modified fang. Their venom gland sits right above the brain.”

The time and effort that went into the paper is extraordinary, starting with medical reports of people injured after encountering venomous fish. After finding out exactly what venomous glangs look like, they created a family tree of all venomous fish, using specimens from natural history museums to trace evidence of venom through closely related species.

“For instance, relatives of yellowtail that people eat as sushi were reported as venomous, and we were able to find venom glands in their spines.”

Deep-sea one-jawed eel is shown with a venomous fang on the roof of the mouth, W. Leo Smith

Deep-sea one-jawed eel is shown with a venomous fang on the roof of the mouth,
W. Leo Smith

Evolutionary traits

However, it’s the evolution of the venom used by fish that mostly interested Smith and his colleagues, with the evolution resulting in opportunities for drug makers.

That’s because these fish live perfectly healthy lives with “super-complicated venoms” that, when deposited on other species, can result in immense pain or even death.

“Venom can have impacts on blood pressure, cause local necrosis, breakdown of tissue and blood, and hemolytic activity — it prevents clotting to spread venom around prey,” said Smith.

According to the team, because fish have to live with their own venom, “there might be helper molecules that protect the fish themselves and help them survive”. He said these also could have therapeutic value to people.

This is the last thing many fishes see, a head-on view of a Venomous Devil Firefish, via W. Leo Smith

This is the last thing many fishes see, a head-on view of a Venomous Devil Firefish, via
W. Leo Smith

Main lionfish image via Shutterstock

Gordon Hunt is senior communications and context executive at NDRC. He previously worked as a journalist with Silicon Republic.

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