Slime eel - the slimiest animal in the world

Slime eels have evolved the ability to use mucus as a defense mechanism to clog the gills of predators in less than a second .

Slime eels ( Myxinidae ) are the slimiest animals on the planet. Their slime can expand 10,000 times in 0.4 seconds. This defense mechanism is very effective in deterring predators like sharks, according to IFL Science .

The slime secreted by eels when fishermen pull them out of the water. (Photo: Flickr).

The slime eel's mucus forms when seawater comes into contact with two different materials secreted by its mucus glands, including mucus sacs that can rapidly swell and burst in the water, forming a sticky network of fibers called intermediate filaments (IFs) . IFs are only 12 nanometers wide but up to 15 centimeters long. They are arranged in wool-like bundles called fibrils.

To unravel the mystery of the slime eel's mucus, a team from the University of Illinois looked at how the filament cells behaved when exposed to seawater in a 2019 paper. They found that the coiled filament began to uncoil around the time of a predator attack (100 to 400 milliseconds), which could be faster if the filament was attached to a surface like the predator's mouth.

The coiled fibers can expand up to 10,000 times their original size, creating a network of fibers that the mucus sacs can connect to create a sticky mass that is difficult to deal with. Exposure to seawater accelerates the transformation because the seawater dissolves the protein glue that holds the coiled fibers in place, releasing the stored elastic energy.

Eels are tough prey for predators, but they can sometimes cause trouble for humans. In 2017, a woman was driving a truck carrying 3,400kg of eels. Traffic police signaled for the driver to stop, but the sudden braking caused the container of eels to spill onto the road. The eels' defense mechanism kicked in, creating a thick layer of slime that covered the road.