Hagfish

Fascinating facts about the Hagfish

• The Atlantic hagfish can tie its supple, eel-like body into a knot, a behaviour that scrapes the thick slime off its skin from head to tail. Forming this knot also lets the animal escape from cramped burrows and gives it the leverage needed to pull prey out of the substrate, compensating for its lack of jaws. The maneuver is a key part of its feeding strategy, allowing it to grip and tear larger food pieces.
• The skin of Myxine glutinosa bears between 88 and 102 pores that constantly release a thick, transparent slime when the animal feels threatened or is feeding. It produces two kinds of slime: a continuously secreted epidermal mucus that guards against pathogens, and an extruded slime released only during feeding, provocation or stress.
• The Atlantic hagfish possesses a blood volume about three times larger than that of other fishes, an adaptation that helps it survive in the low-oxygen, muddy sediments it inhabits. It lives on soft ocean floors ranging from 20 to 1000 metres deep, where oxygen levels can be limited. The enlarged circulatory capacity allows the hagfish to maintain metabolic function in these hypoxic conditions, supporting its scavenging lifestyle on the seafloor.
• The Atlantic hagfish's eyes are devoid of a lens and any pigment, giving them a cornea-like window of uncoloured skin. Because they also lack a vitreous body, experimental work has shown the eyes have no photoreceptive function and the retina is considered functionless. Some electrophysiological tests on a close relative hinted at a possible light response, but the species is effectively blind.
• The Atlantic hagfish tolerates a wide thermal range, surviving water temperatures from freezing 0 °C up to 20 °C, and it is regarded as the most cold-tolerant hagfish, thriving especially at 0-4 °C. However, it cannot endure sudden temperature shifts, and its physiological limits are tightly bound to this range. Salinity tolerance is similarly narrow, with lethal effects below about 31 ppt.

Sources

Every fact above was checked against these pages, and kept only where one of them states it.

• Wikipedia

At a glance

About the Hagfish

Hagfish are among the most ancient vertebrate lineages alive, largely unchanged for 300 million years. They have no jaw, no eyes beyond light-sensitive cells, and no true vertebrae. What they do have is a unique defence mechanism: under threat, they release explosive threads of mucus and water that expand into thick, fibrous slime capable of clogging a shark's gills.

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