The carrion-eating hagfish has been described as the “vacuum cleaner of the ocean”. But it also has another claim to fame: it can see off its attackers in a puff of slime. Zurich scientists are researching how this fast-forming hydrogel could be harnessed for human use.
Jawless and boneless, the hagfish is a rather ugly-looking marine creature that has been around for more than 300 million years.
“They live in all the oceans except the polar seas, in the cold and rather salty waters. They are mainly scavengers, that means they feed on carcasses and dead bodies,” explained Lukas Böni, from the Laboratory of Food Process Engineering at the Federal Institute of Technology Zurich (ETHZ).
So why are the hagfish of interest to researchers at the lab? The answer is in the creature’s slime. When the hagfish is attacked or stressed it secretes vast amounts of the substance as a defence mechanism – as this shark finds out in this clip. It has to back off or face suffocation.
“Hagfish slime is special in many ways,” doctoral student Böni told swissinfo.ch. “It’s the most dilute hydrogel known today. It consists of 99.996% water which is a world record.”
“It’s also a hydrogel which forms extremely fast compared with other hydrogels, such as gelatine, that need time and energy input, so you need to cook it in order to form the gel. Hagfish slime forms in cold water with very little energy input.”
Nappies and contact lenses
Hydrogels are already used in many fields, from plasters to nappies, in food, like the gelatine mentioned above, and even in contact lenses. But none are as efficient and fast-forming as the natural hagfish slime.
“Our overall aim is to understand this efficient gelation mechanism and to transfer this insight to other systems to make hydrogels more effective,” Böni said of the lab’s three-year research project.
The hagfish’s hydrogel has two main components: 15-30 centimetre-long protein threads and mucin, which sits between the threads and makes the slime “slimy”.
The mucus and thread is produced in special ventral glands along the side of the hagfish. When it’s mixed with sea water it expands to create huge amounts of slime.
If you look at magnified pictures of the glandular secrete, as we did during swissinfo.ch’s visit to the lab, you can see these tiny threads coiled up. But how the coiled up thread unravels and forms the slime is not yet fully understood.
You won’t, however, see any hagfish in the Zurich lab. Coming from a landlocked country, the scientists had to look elsewhere for their hagfish - and found them at the Atlantic Park in Ålesund in Norway.
Norway and fishing
“They have become good friends of ours. They help us on a voluntary basis: by going fishing for us or we go with them,” Böni said.
The four-person team visits Norway two to three times a year – the next visit is scheduled for October – to bring back slime samples. The first time the researchers went there, however, they were surprised to be met by a television crew.
But the resulting report had its advantages when it came to doing the official paperwork to take the hagfish samples out of Norway, Simon Kuster, Böni’s supervisor on the hagfish project, told swissinfo.ch.
“All those officials knew about us and they said: just send us all the necessary papers. So it was good and helpful - these crazy Swiss scientists in Norway trying to work with one of their least popular animals.”
Norwegian fishermen hate the hagfish (in this case the Atlantic hagfish, Myxine glutinosa), Kuster explained.
“When they go fishing with nets in depths of 40-50 metres, hagfish will come into the nets and start to eat the fish in the net. So if the fishermen take the nets up too late, all they see is just some skin and bones and some slime in the net. There are millions of these hagfish in the sea there.”
In any case, transporting the hagfish back to Switzerland is almost impossible, the scientists added. Hagfish don’t like captivity. They would also get stressed out by the journey and release slime, suffocating themselves in the process.
So far the researchers have found out that the slime is susceptible to mechanic stresses. They have tried to stabilise it by adding other polymers to ensure that it does not collapse so easily. Their latest research was published in January.
Although there is some time before their research has practical applications, one possible use could be to structure foods, as the slime contains fibres, just as meat does.
“One nice thing is that it would be vegetarian, because when we harvest the slime the fish survives this,” Böni added.
And has anyone from the team actually tasted the slime? Böni admits he has, but as it is basically water it “tastes of the sea” or whatever you mix it with.
The ETHZ team is the only one in Europe looking into hagfish slime so far. A team in Canada has proposed that the slime’s fibres, which are similar to spider silk in being strong and stretchy, could be used to make textiles.
Scientists can learn a lot from nature, Kuster said. He enjoys the pure science of the slime project – observing, making a hypothesis, checking and correcting, coming up with new ideas - as well as the fruitful collaboration with their Norwegian colleagues.
As for Böni, he is pleased he can do something to rehabilitate this ocean ‘hoover’. “Maybe by doing this research it will raise further awareness that the hagfish is actually a very important animal for the ecosystem,” he said. And maybe its slime will be useful to humans, too.
Learning from nature
Biomimicry involves scientists looking at nature and trying to extract the most important things from to make something useful, Simon Kuster says.
Kuster got the idea of looking at hagfish slime after watching a BBC documentary on the hagfish.
Another example of biomimicry is sharkskin. It’s covered by tiny V-shaped scales, called denticles, which reduce drag and turbulence. The principle has been used to make swimsuits which can improve a swimmer’s speed.
Spider webs are also a goal in the research world, as recreating the powerful spider silk could produce durable fabrics. But no one has yet managed this most tricky of tasks.
(Source: Simon Kuster, Smithsonian National Museum of Natural History, Wall Street Journal)