Hagfish a jawless fish. which is an eel-shaped slime producing marine animal. They are also called slime eels because of this slime production. Also, the only known living animal which has a skull but no vertebral column.

Hagfish are a sister group to jawed vertebrates. The Classification of this fish had been controversial Issue was it does not have a spine.

A hagfish image

There were two schemes supporting and reasoning of the issue. The original was that hagfish was a degraded fish that lost the spine through evolution. The alternative was that hagfish was a stage of evolution that precedes the vertebral column(spine). the recent DNA supports the original scheme. they are closely related to lampreys.

Eel-Body of a Hagfish

Hagfish are typically about 50 cm in length. The largest specimen recorded was 4 ft 2 cm in length, while the smallest being of 4 cm. Hagfishes have an elongated ell-shaped body and paddle-like tail. color depends ranging from the species. whether pink, blue-grey or spotted. Eyes are simple eyespots and they are not lensed eyes that can resolve the image. Tooths of a hagfish is made up of keratin.

Slime from this slime eel

hagfish are long and in the shape of a worm. they can exude plenty of milky and fibrous slime. when captured and held like by the tail. they secrete microfibrous mucus. which can expand into up 20 liters with sticky material when combined with water. if they remain captured they will tie themselves in an overhand knot.

A hagfish knot

The slime of the hagfish is proven to attack fish’s gills. The mucus of the fish would clog the predator’s gills. Disabling the ability to respire. due to that, the predator has to throw out the hagfish to avoid suffocation.

Nervous system

The complexity of this fish brain has been an issue of debate since the late 19th century, with some morphologists believing that they do not possess a cerebellum. while some believe it continues in the midbrain.

Eye of the hagfish

The hagfish eye lacks a lens, some muscles, and cranial nerves. Its eyespot can detect light when present but cannot resolve detailed images.

Cardiac function,circulation and fluid balance

These fishes are known to have one of the lowest blood pressures among the vertebrates.

One of the most primitive types of fluid balance found is among these creatures, whenever a rise in extracellular fluid occurs, the blood pressure rises and this, in turn, is sensed by the kidney, which excretes excess fluid. They also have the highest blood volume to the body mass of any chordate, with 17 ml of blood per 100 g of mass.

The hagfish circulatory system has been of considerable interest to evolutionary biologists, who first believed that the hagfish heart was not innervated like that in jawed vertebrates. Further investigation revealed that this fish did have a true innervated heart.

The hagfish circulatory system also consists of multiple accessory pumps throughout the body, which are considered auxiliary “hearts”.


Very little is known about hagfish reproduction. Embryos are difficult to obtain for study, although laboratory breeding of the Far Eastern inshore hagfish has succeeded. Some are thought to be hermaphroditic. Having both an ovary and a testicle. in some cases, the ovary remains non-functional till the fish reach a particular age or particular environmental stress. These two factors in combination suggest that the survival rate of this fish is high. Depending on the species the hagfish can produce 1 to 30 tough, yolky eggs. these tend to aggregate due to velcro-like tufts at either end. Hagfish do not have a larvae stage, while the lamprey has one and it’s a quite long one. The development of this fish embryo is retarded in comparison to other jawless vertebrates, taking as long as 11 months before hatching.


A single fossil of a hagfish shows a little to none evolutionary change that occurred in 300 million years.in recent years, this fish has become an area of study for genetic analysis.


In most of the world, this fish is not eaten but in korea this fish is a value food, where it is generally skinned, coated in spicy sauce, and grilled over charcoal or stir-fried. It is especially popular in the southern port cities of the peninsula, such as Busan. Japan eats the inshore hagfish. which is found in the northwest pacific. As hagfish slime binds vast amounts of liquid even at low temperatures, it was proposed as an energy-saving alternative for the production of tofu that does not require heating.


This fish skin, used in a variety of clothing accessories, is usually referred to as “eel skin”. It produces a particularly durable leather, especially suitable for wallets and belts.

My take from this

This topic is in general quite interesting. Thinking about the things the ocean holds is both fascinating and scary. A fish capable of producing enough slime to fill 20 a 20-liter bucket is a lot.

which has so many special abilities.A species that hasn’t evolved for 300 million years.



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