Hagfish are equipped with four rows of keratinous teeth that they can use to grasp and bite flesh from dead animals or live prey.
Credit: Museum of New Zealand Te Papa Tongarewa
Te Papa scientist Carl Struthers, holding the world’s second-largest hagfish specimen, freshly caught off White Island at a depth of 912 m. The giant hagfish, Eptatretus goliath, is only known from New Zealand, and can grow up to 1275 mm long, weighing up to 6.2 kg.
Credit: Museum of New Zealand Te Papa Tongarewa
SYDNEY: Hagfish were long assumed to be sedate, scavenger fish, but new research has revealed that they may be efficient hunters who use slime against prey and other predators alike.
Also known as the 'snot eel', hagfish have existed morphologically unchanged for 300 million years. Biologists have been studying them since the 1700s and long believed that they survive by trawling the bottom of the ocean for scraps of dead or dying fish. However, new video footage captured off the coast of the Great Barrier Island in New Zealand suggests otherwise.
"Hagfishes have developed an extremely efficient defence mechanism by secreting slime to instantly choke any predators," said biologist Vincent Zintzen, co-author of the paper recently published in Scientific Reports from the Museum of New Zealand Te Papa Tongarewa in Wellington.
300 million years of history
The hagfish comes from the myxinidae family of slime-producing marine animals and is found all over the world in temperate environments. Hagfish fossils date back 300-550 million years, and are considered one of the most primitive vertebrates known, living or extinct.
It commonly lives within a relatively wide range of ocean, between 50 and 700m below sea level, and it is believed to be able to absorb nutrients of its meal through the skin. Hagfish have 90-200 pores along their body through which they excrete protein threads and other matter.
When combined with seawater, the protein threads swell up and creates masses of slime, which researchers have been trying to engineer as a nylon alternative. In order to clean itself of the slime, the hagfish then contours its body into an overhand knot and slips through itself, de-sliming in the process.
Not just a scavenger
Previously, the hagfish had only even been recorded feeding off the remains of dead fish on the ocean floor. Scientists had long hypothesised about how the hagfish had survived for millions of year on scavenging alone.
Many believed it had some ability to hunt and must have an effective defence mechanism they had yet to discover. It wasn't until the footage from this study was taken that the hypothesis could be proven.
"We thought they ejected slime en masse," said co-author Euan Harvey from the University of Western Australia's Oceans Institute in Perth. However, what happens is that the slime is excreted directly into the mouth of the predator, only from those glands located where the predator attacked. Harvey said that the team's research revealed that the slime coats the gills of the target to suffocate them.
More active than thought
Hagfish were also thought to be relatively sedate fishes, according to Chris Glover from the University of Canterbury in New Zealand, who was not involved in the study. "They may be more active than we thought," Harvey said of the footage, adding that biologists may need to rethink their previous assumptions on hagfish hunting patterns.
The video footage was taken using a video unit Harvey developed during his early research years in New Zealand and adapted by Te Papa to work at greater depth. It allows biologists to survey underwater creatures using bait and a video camera without causing any destruction to their habitat.
Traps, trawling and long lines have long been used by biologists for sampling populations, but they have also lead to harming the natural environment. "It's not destructive and it means we can sample inside marine parks," said Harvey.
