The Goliath Hagfish

Details about Hagfish
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Hagfish are eel-shaped marine fish.

Despite their slime production, they have a skull – one of the only living creatures with a skull! They also have rudimentary vertebrae.

You can learn more about them here.

This article focuses on the Goliath Hagfish, but you can also learn about other species of hagfish.


Myxinidae Goliath Fish

The hagfish is a type of slime-producing marine fish. It is one of only a few living animals with a skull.

Despite their skull, hagfish have vertebrae. These rudimentary vertebrae allow it to breathe, which is crucial for survival.

The Myxinidae of Haga are considered the most primitive vertebrates, and there are over 70 species worldwide.

These fish play an important role in the deep-sea food web and are important prey for sharks and cephalopods. But, their exact role in the ocean is not yet well understood.

Despite their elusive nature, the hagfish family has been around for 300 million years. Adaptation and a thick layer of slime help these fishes survive.

They feed on various types of fish, both dead and alive. Their unique scaly bodies and slimy skin protect against predators and help them defend themselves.

The hagfish is unique among marine fishes in that it is a very sensitive species to changes in salinity.

It is the only known vertebrate with isosmotic body fluids, which have the same osmolality and total osmotic pressure as seawater.


Hagfish are large, slimy fish with thick mucus exudations. Their long bodies contain up to 70 or 200 slime glands, which contain thread-like cells that add tensile strength to the slime.

These fibers are biodegradable and could potentially be used to stop blood flow in accident victims and surgical patients.

Although the classification of hagfishes is difficult, recent studies show that there are three distinct subfamilies.

These subfamilies are mainly based on morphology, which is often quite similar in different species.

Hagfishes are found in all oceans except the Red Sea. They mainly inhabit the benthic region and are native to coastal waters around Asia.

Hagfish can move through the water in a snake-like motion. They also have slime glands on their sides that produce a thick, jelly-like substance.

Hagfish use slime as a defense mechanism. Hagfish slough off their slime by knotting their bodies, sneezing, or traveling in a spiral snake-like motion.


The eyes of hagfish are small and unpigmented. They lack features that distinguish them from other jawed vertebrates, such as a lens, extra-ocular musculature, and a duplex retina.

Instead, hagfish have semi-transparent skin covering their eyes. Although the hagfish’s eyes lack a lens, they do have photoreceptors and RGCs.

The body of a hagfish is eel-like and can grow up to half a meter (18 inches) in length. The largest hagfish species is the Eptatretus goliath, with a specimen measuring 127 centimeters (44 inches).

Other large hagfish species are Myxine kuoi, which can grow up to 18 centimeters long.

The hagfish lack a dorsal fin and jaw, making it look like an eel. The hagfish circulatory system is a simpler one than that of vertebrates.

It resembles the circulatory systems of some worms. The hagfish’s circulatory system consists of the main pump and three types of accessory hearts.

The portal heart transports blood from the intestines to the liver. The cardinal heart pumps blood from the head to the body, and the caudal heart pumps blood from the kidneys to the body.


Hagfish live in the Pacific Ocean. They are marine scavengers with pairs of dental plates. They feed on the decaying bodies on the sea floor.

They also eat fish that have been caught in fishing nets.

These fish are commonly found in large bodies of water and have no known negative effects on humans.

The hagfish is part of the family and is divided into six genera. They share a common characteristic, having no jaws.

The hagfish is not a true eel, using a pair of rasps on its tongue to tear food.

It also has a pineal eye in its topmost head, vestigial eyes on either side, and a single terminally located nostril near its mouth. Hagfishes have good senses of touch and smell.

The hagfish produces mucus that is thick and dense. This slime can be used to make materials like helmets and kevlar.


Size of Hagfish

In this study, the size of the head of an Atlantic hagfish was measured using video and still images. Three hagfish were studied. One moved through the slit on its tail first.

This fish’s body width decreased as it approached the slit on its trailing side and increased as it emerged from the other side. The same process was repeated for the remaining two hagfish.

The size of a hagfish can vary widely, and its gender varies depending on the season. One study used twenty videos of Atlantic hagfish and 28 videos of Pacific hagfish.

This study has shown that the average size of hagfish depends on the hole size. This fish has a large population in their local waters.

The larger a hagfish is, the more cells it has. This means it can withstand more force before breaking, which might be a beneficial evolutionary advantage.

Larger hagfishes can also produce larger volumes of slime, which can serve as a defensive deterrent to larger predators.


The diet of hagfish differs from that of other fish. These creatures are carnivorous, feeding on small invertebrates and carrion.

Their preferred habitats include caves on the ocean floor and deep ocean waters. The hagfish diet varies depending on its habitat.

The diet of hagfish is rich in lipids, an essential energy source for these animals.

The hagfish’s intestinal tract is characterized by highly elevated lipase activity.

Lipases are enzymes required for the digestion and assimilation of dietary lipids. In hagfish, lipase activity is accentuated in the anterior part of the digestive tract.

The digestive enzymes of hagfish differ from those of other fish.

While most digestion activity occurs in the hindgut region, hagfish also exhibit high enzyme activity in the anterior and posterior portions of the alimentary canal.

The activity in these segments is decreasing in vertebrates but not in hagfish. This variable expression of enzymes may indicate compartmentalization of gut function.

Embryo development

Hagfish embryo development can be studied by using modern techniques.

Hagfish embryos show the topographic relationship between superficial endoderm and differentiating head structures.

The newly formed neural tube rests directly on the cellular layer of the endoderm that binds the yolk. During development, most of the brain remains in contact with the yolk endoderm.

Several studies of hagfish embryo development have been conducted since the late nineteenth century. However, hagfish embryos are notoriously difficult to obtain.

Early investigations relied on material obtained from small field specimens.

These difficulties made hagfish embryology difficult.

However, in the 20th century, scientists started using small field samples to conduct embryology research.

Embryos of hagfish were dissected to determine the position of certain structures. The earliest embryos had no head fold, a shallow infundibulum, and a ventral pouch-like swelling.

The position of the cross-section in Figure 4 indicates the embryo’s position.

By comparison, the older hagfish showed several changes in their embryos, including developing the head fold and the first archenteric space.

The thickened endoderm beneath the infundibulum was also noted.