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Hagfish

life science Maturity 5-7 Next article →

Hagfish are unique marine animals belonging to the class Myxini. They are often called slime eels because of their eel-shaped bodies. These creatures act as both predators and scavengers in the ocean.

Eptatretus stoutii
Eptatretus stoutii

They are biologically unusual because they possess a skull but lack a vertebral column. Instead of a bony backbone, they have rudimentary vertebrae and a structure called a notochord. Genetic evidence shows they are closely related to lampreys. Together, these two groups form a superclass known as Cyclostomi.

Hagfish skull Fig 74 in Kingsley 1912
Hagfish skull Fig 74 in Kingsley 1912

Hagfish use a remarkable defense mechanism involving specialized mucous glands. When the animal is threatened, it releases large amounts of milky, fibrous slime. This slime expands to 10,000 times its original size in only 0.4 seconds.

Hagfish Slime Predator Deterrence
Hagfish Slime Predator Deterrence

The slime contains thin protein fibers that make it very durable and flexible. This substance is a viscoelastic material rather than a simple gel. When the slime enters the water, it can clog the gills of a predator. This makes it difficult for the predator to breathe, forcing it to release the hagfish.

Pacific hagfish Myxine
Pacific hagfish Myxine

To manage their own slime, hagfish perform a unique behavior. They can tie their bodies into an overhand knot. They then slide this knot from their head toward their tail. This movement allows them to scrape the slime off their own bodies. This process is necessary to restore their own gill function after a slime release. The slime's viscosity changes depending on how it is moved. It becomes thicker during certain flows to clog gills, but thinner during the knot-scraping motion.

There are different types of hagfish found in various oceans. The Atlantic hagfish belongs to the subfamily Myxininae. The Pacific hagfish belongs to the subfamily Eptatretinae.

Eptatretus stoutii 1
Eptatretus stoutii 1

These two groups have distinct physical differences. Pacific hagfish have muscle fibers embedded directly in their skin. They also tend to rest in a coiled position. In contrast, Atlantic hagfish usually remain in a stretched position. Their colors vary by species, ranging from pink to blue-grey, and may include black or white spots.

Hagfish have a very long history on Earth. The oldest known stem group hagfish appear in the fossil record from the Late Carboniferous period. This was approximately 310 million years ago. Modern representatives of the group were first recorded around 100 million years ago. This occurred during the mid-Cretaceous period.

Eptatretus polytrema
Eptatretus polytrema

Their bodies have remained effective for millions of years. They are quite diverse in size. The largest species is Eptatretus goliath, with a specimen recorded at 1 meter. Other species, such as Myxine kuoi, are much smaller. Some individuals can be as small as 10 centimeters.

The biology of the hagfish is highly specialized. They have a cartilaginous skull and a single nostril. Instead of traditional jaws, they use two pairs of horny, comb-shaped teeth. These teeth are on a plate that can move forward and backward to grasp food.

Pacific hagfish feeding 01
Pacific hagfish feeding 01

Their eyes are simple eyespots that detect light but cannot form clear images. This is considered a degenerative trait from ancestors with complex eyes. Their circulatory system is also unique. They have one of the lowest blood pressures among vertebrates. They also maintain a very high blood volume relative to their body mass.

Scientists study hagfish to understand the evolution of complex life. Their nervous systems help biologists learn about the origins of the vertebrate brain. For example, hagfish neurons lack myelin, which is a fatty layer found in many other animals.

Dorsal, left lateral views of dissected hagfish brain
Dorsal, left lateral views of dissected hagfish brain

Even their slime is being researched for modern technology. The protein filaments in the slime are being studied as a possible material for body armor. These alpha-keratin proteins become very stiff when they are stretched. This makes the material extremely strong, which could lead to new types of protective gear.

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🖼️ Images & Media (13)
File:NIE 1905 Hagfish - Myxine glutinosa.jpg
NIE 1905 Hagfish - Myxine glutinosa.jpg
File:Eptatretus stoutii.jpg
Eptatretus stoutii.jpg
File:Hagfish Slime Predator Deterrence.jpg
Hagfish Slime Predator Deterrence.jpg
File:Eptatretus stoutii 1.jpg
Eptatretus stoutii 1.jpg
File:Dorsal, left lateral views of dissected hagfish brain.jpg
Dorsal, left lateral views of dissected...
File:Hagfish trunk.jpg
Hagfish trunk.jpg
File:Hagfish skull Fig 74 in Kingsley 1912.png
Hagfish skull Fig 74 in Kingsley 1912.png
File:Black_hagfish,_Eptatretus_deani_gonads_01.jpg
Black_hagfish,_Eptatretus_deani_gonads_01.jpg
File:Eptatretus polytrema.jpg
Eptatretus polytrema.jpg
File:Eptatretus cirrhatus (New Zealand hagfish).gif
Eptatretus cirrhatus (New Zealand hagfish).gif
File:Pacific hagfish feeding 01.jpg
Pacific hagfish feeding 01.jpg
File:Pacific_hagfish_Myxine.jpg
Pacific_hagfish_Myxine.jpg

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