Atlantic Hagfish

The Atlantic hagfish (Myxine glutinosa) is a jawless, eel-shaped marine fish belonging to the ancient class Myxini, a lineage that split from other vertebrates over 300 million years ago. It inhabits cold, deep waters of the North Atlantic Ocean, from the eastern coast of North America to the coasts of Europe and Scandinavia. Hagfish are best known for their extraordinary ability to produce large volumes of thick, viscous slime from specialized pores along their body when threatened, which can clog the gills of would-be predators. They lack a true backbone, jaws, and paired fins, instead possessing a skull made of cartilage and a notochord. Hagfish play an important ecological role as scavengers of dead and dying animals on the deep seafloor.

Atlantic hagfish have a soft, worm- or eel-like body plan that is unmistakable once its key features are noted.

Key field marks:

• Elongated, scaleless, cylindrical body in pinkish-grey to purple-brown tones
• No jaws — instead a small round mouth surrounded by fleshy barbels and rasping tooth-like plates
• No paired pectoral or pelvic fins; only a low fin fold along the tail region
• Small, degenerate eye spots covered by skin rather than functional eyes
• A single nostril at the tip of the snout
• Rows of visible mucus pores running along each side of the body, the source of its defensive slime
• Adults typically 40-60 cm long

Its lack of jaws, fins, and scales, combined with the mucus pore rows, readily separate it from true eels and lampreys, the latter of which have a circular toothed sucker mouth rather than barbels.

Atlantic hagfish live on or near soft muddy and silty seafloor habitats of the continental shelf and upper slope across the North Atlantic Ocean, from depths of roughly 20 to over 1,000 meters, typically in cold water below about 10°C. Their range extends from the eastern coast of North America to Iceland, the British Isles, Scandinavia, and the Mediterranean. Hagfish spend much of their time partially or fully buried in soft sediment, emerging to scavenge or to enter carcasses on the seafloor. They favor dim, low-light deep environments and generally avoid brightly lit shallow waters, making them rarely encountered outside of deep trawls or bottom cameras.

Atlantic hagfish are primarily nocturnal, solitary scavengers that locate dead or dying animals on the seafloor using well-developed chemical and tactile senses, since their eyes are non-functional. They are capable of burrowing into a carcass to feed from the inside and can also prey on small invertebrates. When threatened or attacked, a hagfish rapidly releases mucus-producing slime that expands enormously in seawater, clogging the gills of predators such as sharks, and it can then tie its own body into a knot to slide free of the slime and any residual grip. Hagfish reproduce by laying a small number of large, tough-shelled eggs on the seafloor, with no larval stage and no parental care. Their scavenging activity helps recycle nutrients from carcasses back into the deep-sea ecosystem.