‘Snot eel’ blasts predators with slime

By Natalie Muller 25 June 2014
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The eel-like hagfish slimes its predators in an unusual defence mechanism and it’s been captured on video.

THE EEL-LIKE HAGFISH is notorious for using its unique mucus-oozing abilities when it feels threatened. But for the first time, scientists have filmed this primitive creature squirting the noxious slime to escape from sharks and other predators.

The footage confirms suspicions that hagfishes, also known as ‘snot eels’, choke predators with this gill-clogging substance when they’re under attack.

Scientists from the University of Western Australia (UWA) in Perth and at both Massey University and the Te Papa museum in New Zealand, installed baited video cameras in deep water off NZ’s Three Kings and Great Barrier Islands. The footage (above) shows a shark sinking its teeth into the hagfish, then darting away after getting a dose of slime.

“As soon as it is attacked, the hagfish releases a mucus-like substance from a battery of slime glands, which makes predators gag before quickly retreating,” says Professor Euan Harvey of the UWA Oceans Institute. “While scientists have known about the protective qualities of the hagfish’s slime for some time, this is the first time anyone has been able to capture it in the act of repelling a predator.”

Hagfish survives deep sea

The hagfish is almost blind, has no jaw, and is thought to be among the most ancient of living vertebrate species. They’re known mainly as scavengers that use tooth-like rasps to feed on dead and decaying fish on the ocean floor. Hundreds of pores run along its body, capable of excreting copious amounts of slime, which expands into sticky goo when it mixes with water.

Studying this elusive creature in its natural habitat is extremely difficult. Professor William Gladstone, a marine biologist at the University of Technology, Sydney, says that because they live so deep, much of what we know about them is based on captured or dead specimens. “Advances in the technology of deploying underwater video cameras in deep water and stereo imaging have overcome this barrier,” he says.

Animal physiologist Dr Chris Glover from the University of Canterbury in Christchurch has been involved in various studies of the hagfish. While the video shows just how quick and effective the slime mechanism works against predators, some gill-bearing animals can still eat hagfish. For example, previous studies have found hagfish tissue in the gut of a shark, he says. “So I guess the question now is, how the hell do they actually manage it?”

A hagfish shows off its teeth. (Credit: Te Papa Museum)

Hagfish: not just a slimy scavenger

The team of scientists was surprised when the video footage showed the hagfish not only defending themselves from predators, but also actively attacking other fish. Euan says this is the first time predatory behaviour has been witnessed in this family, known for primarily being scavengers.

“The footage showed it has an unusual method of burrowing into sand in pursuit of a red bandfish and knotting its tail for extra leverage,” he says. “It then captures the prey before unknotting itself and emerging from the sand.” 

Chris says active hunting behaviour has been suspected in hagfish because of previous studies examining their gut contents. “This study confirms what has been previously thought, and as such it is an important and really nice compliment to the existing literature, rather than a ‘sea-change’ in our thinking of hagfish biology.” He says a further point of study would be to determine how widespread this form of hunting is across the many different hagfish species.

The fossil record suggest that hagfish haven’t changed much over the past 500 million years. William says this latest study using video recording technology is likely to inspire other scientists to discover more about the reproduction and social behaviour of these mysterious and ancient creatures.

The research was published in Scientific Reports, part of the Nature group of journals.

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