The Pacific hagfish secretes bucket-loads of slime.
Credit: Timothy M winegard
SYDNEY: Being a marine biologist can be tough, especially if one of your subjects happens to be a tiny fish with an incredible defence mechanism.
"If you try to grab one of these things, they give off a litre of slime" says biologist Douglas Fudge from the University of Guelph in Ontario, Canada.
The eel-like hagfish that Fudge studies weighs about 150 grams, but can produce up to about 25 litres of slime, suffocating a potential marine predator by clogging their gills.
Ties a knot to 'de-slime'
The pool of goo is not a problem to the hagfish itself; when it's time to 'de-slime' it simply ties itself in an overhand knot and passes the knot down its body, wiping away the slime as it goes.
Hagfish is actually the name for a group of about 70 eel-like creatures that live in dense groups in the muddy ocean floors.
When they aren't spraying other creatures with slime, they're feasting on worms or whatever falls to the floor - though they're also known to burrow into dead or dying fish by eating a hole through the flesh or entering through the mouth or anus before eating them from the inside out.
Skull, but no jaw, no backbone
They have a skull but no jaw and, unlike most fish, no backbone. It may sound haphazard, but it's a successful body plan: the oldest fossil is 330 million years old, and the creature hasn't changed much since.
The hagfish may be a sister group to all vertebrates, though there's debate over the timing of the split, which occurred somewhere between 530 and 390 million years ago.
They're so ancient that they even provided a 'missing link' in the evolution of the eye, which occurred in a short, 30-million-year period around the time the two lines split.
Mucus-like cells trap seawater
Hagfish have a primitive eye-like structure beneath an opaque eye-patch on either sides of the head, but they behave as though they are blind, according to Shaun Collin from the University of Queensland.
But their most useful quality is the mountain of slime they produce. The secret weapons of this mass-defying trick are special 'thread cells' in hagfish slime secretions.
These thread cells contain fibres just 0.002 millimetres wide that are wound like balls of yarn until secreted, when they unravel to 12 cm in length. It's the combination of these fibres with more mucus-like cells that traps seawater and turns a few grams of secretion into litres of slime.
Fudge is studying the constituent proteins with the hope of developing a commercial fibre that could replace petroleum-derived nylon. Not that he wants to see armies of hagfish farmed for slime - he hopes to genetically engineer bacteria to produce the fibres on a large scale. "The thing that keeps me going is replacing nylon," he says. "If we could make a dent in our consumption of nylon, that would be a great thing."
