hagfish

A hagfish is an eel-like marine animal that lacks jaws and a true backbone, making it one of the most primitive vertebrates.

Hagfish are known for producing enormous quantities of slime when threatened—a single hagfish can fill a bucket with mucus in minutes.

They feed mainly on dead or dying fish, burrowing into carcasses to consume them from within.

Despite their off-putting habits, hagfish leather is used commercially.