By Henry Workman
Research from New Zealand’s Massey University and Te Papa has produced footage revealing the hagfish’s one-of-a-kind defense mechanism. When threatened the creature will expel a mucus-like substance which interferes with the gill functioning of predators, causing them to gag and swim away. The study also yielded insight into the hagfish’s own predatory technique, which involves entering holes in the ocean floor to pursue burrowing prey.
The hagfish, often referred to as the “slime eel” (though not an eel), has been a recurring subject of recent research and general interest due to unique anatomical and behavioral traits. It is considered more primitive compared to other species of modern fish, having survived relatively unchanged for upwards of 300 million years. The slime defense, which helps protect against a diverse range of natural enemies, may help account for the species’ prolonged success. Studies often focus on relationships to other marine animals, both living and extinct, as well as the significance of now rare traits such as the primitive eye.
Hagfish are widely distributed throughout the world’s ocean depths, making them an important part of the marine ecosystem. However, observation in their natural habitat is difficult and mysteries concerning their behavior and life cycle remain. They have been established primarily as scavengers of the seafloor, entering sunken carcasses such as those of whales through the mouth or other opening and eating from the inside out. The vertically aligned opening of their mouth is lined with rows of “toothplates,” used to tear away chunks of flesh.
The slime hagfish are well known for is secreted from between 90 and 300 pores along the length of its body. It remains coated in a layer of slime and can completely alter the consistency of the water in a five gallon bucket just minutes into being kept inside one.
The new documentation contains over 1000 hours of footage taken in waters around New Zealand using bait to draw hagfish near underwater cameras. Demonstrated is the long suspected defensive role of the substance as the hagfish drives away predators. The sudden, rapid release of slime occurred locally at the location of attack and resulted in the immediate retreat of many potential predators. In each instance, both animals appeared to come away from the encounter unharmed. Bait also appeared to take on a coating of slime, hinting at a possible role it may hold in keeping other species from sharing a food source.
In addition to shedding light on the role of slime, the footage contains rare examples of the hagfish’s hunting technique. As it turns out, it makes use of the unique ability to form a knot with its body. This behavior has already been established for other purposes, such as generating leverage needed to tear off pieces of food, as well as helping the hagfish clear its own body of a built-up slime. When the hagfish locates the burrow of red bandfish using specialized feelers, it enters and shortly thereafter remains almost still for a period. It is suspected that doing this may suffocate prey due to the buildup of slime in surrounding water. Finally, the prey is extracted from its hiding place using the additional leverage provided by the knotting technique.
The open-access article was published in Nature.
Copyright © 2011 by Marine Science Today, a publication of OceanLines LLC