Hagfish

Hagfish, commonly called slime eels, are jawless marine vertebrates of the order Myxiniformes within the class Myxini. They are among the most primitive surviving vertebrates. Hagfish lack jaws, true paired fins, and a vertebral column. They have a cartilaginous skull and a persistent notochord. The body is eel-like, typically 40–80 cm long, with scaleless skin. A circular mouth is ringed with keratinous, tooth-like plates and is surrounded by barbels and a single pair of nostrils.

Hagfish are best known for producing copious slime from glands along their sides when irritated. In seawater the slime expands into mucus that can clog gills of potential predators, serving as a defensive mechanism. They are primarily scavengers, feeding on dead or dying animals, though some species will opportunistically prey on invertebrates. They possess a rasping tongue and tooth plates for tearing tissue. A notable behavior is knotting: hagfish can form a tight knot with the body to gain leverage during feeding or to help remove slime.

Habitat and ecology: Found in cold, marine waters worldwide, often on or near the sea floor at various depths. They play a role in nutrient cycling as scavengers and are adapted to low-oxygen or crevice-rich environments.

Reproduction and life history are poorly understood; available information is limited.

Humans interact with hagfish as bycatch in some fisheries, and their slime and biology have attracted scientific interest for biomaterials and insights into vertebrate evolution.