There is a crab with a rough, almost fuzzy appearance because its entire body is covered with short hairs and fine spines.

This crab is known as the Hair Crab.

The Hair Crab is a cold-water species that lives in the northern Pacific Ocean. It occurs around the east coast of Korea as well as near Japan, the Bering Sea, Alaska, and other northern waters. In Japan, it is especially famous as Kegani, where it is highly valued as a premium seafood because of its sweet meat and rich-tasting internal organs.

Its scientific name is Erimacrus isenbeckii.

In this article, we’ll explore the Hair Crab’s appearance, habitat, diet, molting, reproduction, life cycle, and importance as a food resource.

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What Is the Hair Crab?

The Hair Crab is a marine crustacean belonging to the order Decapoda.

Its scientific name is Erimacrus isenbeckii, and it is commonly known in English as the Hair Crab or Horsehair Crab.

Basic information includes:

• Common name: Hair Crab / Horsehair Crab
• Scientific name: Erimacrus isenbeckii
• Order: Decapoda
• Habitat: Seafloor environments in cold waters
• Main distribution: East coast of Korea, Japan, Bering Sea, Alaska, and surrounding areas
• Depth: Approximately 15–300 m
• Preferred bottom: Sand, mud, gravel, and mixed seafloor
• Notable feature: Dense hairs and spines covering the body
• Importance: Valuable edible marine resource

The Hair Crab is a cold-water crustacean well adapted to low-temperature marine environments.

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Appearance

The name “Hair Crab” comes from the dense hairs and bristles covering its body.

Short hairs and fine spines are present not only on the carapace but also on the legs.

Typical physical characteristics include:

• Broad, rounded carapace
• Pinkish, yellowish-brown, or brown body coloration
• Dense short hairs covering the body
• Rough and uneven shell surface
• Strong claws
• Walking legs covered with hairs and spines
• Two prominent projections toward the front of the carapace

Live individuals may appear pale pinkish or brownish, while the hairs are often darker.

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Why Does the Hair Crab Have So Much Hair?

The dense hairs covering the Hair Crab are not merely decorative.

These bristles can contribute to sensory functions by helping the crab detect water movement and physical contact around its body.

They are also one of the species’ most distinctive adaptations to its cold-water benthic environment.

The underside and legs may appear especially hairy when examined closely.

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Size

The Hair Crab is a fairly substantial crab rather than a tiny species.

Adults may have a carapace length of roughly 10 cm or more, with some individuals becoming considerably larger.

Large specimens can weigh around or above 1 kg, although size varies depending on sex, age, habitat, and food availability.

Unlike snow crabs or king crabs, Hair Crabs do not have extremely long legs.

Instead, they have a compact, heavy body with relatively thick and sturdy legs.

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Where Does the Hair Crab Live?

Hair Crabs mainly inhabit the cold waters of the North Pacific.

In Korea, they are associated especially with the eastern coast.

Their range also includes:

• Waters around Hokkaido, Japan
• Sea of Okhotsk
• Bering Sea
• Waters around Alaska
• Russian Far East
• Northern Japanese waters

They are especially associated with cooler northern marine environments.

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What Type of Seafloor Does It Prefer?

The Hair Crab is a benthic crustacean, meaning it spends most of its life walking on the seafloor rather than swimming continuously in open water.

It is commonly found on:

• Sandy bottoms
• Muddy bottoms
• Mixed sand-and-mud areas
• Gravelly bottoms

It is generally more closely associated with soft-bottom habitats than with steep rocky reefs.

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A Crab That Prefers Cold Water

The Hair Crab is a typical cold-water species.

It is better adapted to low water temperatures than to warm tropical conditions.

Young larvae are also highly sensitive to water temperature.

Because of this, environmental temperature can strongly influence survival, growth, and reproduction.

This is one reason why Hair Crabs are closely associated with northern seas and deeper, colder coastal waters.

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What Does the Hair Crab Eat?

The Hair Crab is an omnivorous benthic feeder with strong carnivorous tendencies.

Depending on local conditions, it may feed on:

• Small crustaceans
• Polychaete worms
• Mollusks
• Small benthic animals
• Animal remains
• Organic matter on the seafloor

It uses its claws to capture food and its mouthparts to break it into smaller pieces.

Diet can vary depending on body size, season, and habitat.

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Do Hair Crabs Eat Each Other?

Cannibalism can occur in many crustaceans, especially when food is limited or when large and small individuals are kept together.

Hair Crabs can also show this behavior under certain conditions.

Individuals are especially vulnerable immediately after molting because the new shell is still soft.

During this period, another crab may attack and eat the freshly molted individual.

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How Does the Hair Crab Grow?

Like other crustaceans, Hair Crabs cannot continuously expand inside a hard shell.

To grow, they must periodically shed the old exoskeleton through molting.

The basic process is:

Old shell → Molting → Soft new shell → Body expansion → Shell hardening

Immediately after molting, the new shell is soft and the crab is highly vulnerable.

Over time, the shell hardens and the crab returns to normal activity.

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Can Lost Legs Grow Back?

Like many crabs, Hair Crabs can regenerate lost legs over successive molts.

If a leg is lost because of injury or predator attack, a smaller replacement may begin to develop.

After several molts, the regenerated limb can become larger and closer to its original size.

However, regeneration requires considerable energy and can take a long time, especially in older crabs that molt less frequently.

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Reproduction

Hair Crabs reproduce sexually, and females carry fertilized eggs attached beneath the abdomen.

The species is known for having a relatively long reproductive cycle.

In some populations, the female reproductive cycle can extend over roughly two years, including molting, mating, spawning, brooding, and hatching.

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How Does the Female Protect the Eggs?

After fertilization, the eggs remain attached beneath the female’s abdomen.

She carries and protects them until they hatch.

Embryonic development can be very slow in cold water.

In some observations, the eggs have taken close to a year to complete development before hatching.

This slow reproductive process reflects the low-temperature environment in which the species lives.

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Life Cycle

The Hair Crab’s basic life cycle is:

Egg → Zoea Larva → Megalopa → Juvenile Crab → Adult

The young do not hatch as tiny versions of adult crabs.

Instead, they first emerge as planktonic larvae that look completely different from adults.

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Zoea Larvae

Hair Crabs are known to pass through five zoeal stages.

Zoea larvae look very different from adult crabs and spend time drifting in the water column.

They feed on very small organisms and grow through repeated molts.

With each molt, the body becomes larger and more developed.

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Megalopa Stage

After completing the zoeal stages, the larva enters the megalopa stage.

At this point, the animal begins to look more crab-like.

After another molt, it becomes a juvenile crab and gradually adapts to life on the seafloor.

Water temperature has a major influence on larval survival and development.

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Natural Predators

Young Hair Crabs can be eaten by a variety of marine predators.

Potential predators include:

• Cod and related fish
• Large predatory fish
• Octopuses
• Larger crustaceans
• Other seafloor predators

Hair Crabs defend themselves with their hard shells and strong claws.

However, immediately after molting, they are much more vulnerable.

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Hair Crab vs. Snow Crab

Both Hair Crabs and Snow Crabs live in cold waters and are popular seafood species, but they look very different.

Hair Crab

• Dense hairs covering the body
• Rounded, thick carapace
• Relatively short and sturdy legs
• Heavy, compact appearance
• Famous for rich internal organs as well as meat

Snow Crab

• Extremely long, slender legs
• Wider overall body span
• Large proportion of edible leg meat
• Known for mild, sweet flesh

The Hair Crab has a more rounded and hairy appearance, while the Snow Crab is immediately recognizable by its long legs.

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Hair Crab vs. King Crab

Hair Crabs and King Crabs differ not only in appearance but also in biological classification.

The Hair Crab is a true crab in the infraorder Brachyura, while king crabs belong to a different lineage more closely related to hermit crabs.

Hair Crab

• Scientific name: Erimacrus isenbeckii
• Rounded carapace
• Dense hairs on the shell and legs
• Shorter, stronger legs
• True crab

King Crab

• Includes several species in the king crab family
• Much larger body and longer legs
• Commonly sold as “king crab”
• Evolutionarily closer to hermit crabs

Therefore, despite both being called crabs, they are not especially close relatives.

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Why Is the Hair Crab Popular as Seafood?

The Hair Crab may look smaller than a King Crab or Snow Crab, but it is highly valued for both sweet meat and rich internal organs.

In Hokkaido, Japan, it is considered one of the most popular premium crab species.

The meat is tender and naturally sweet, while the internal organs inside the shell are known for their deep, savory flavor.

In Japan, Hair Crab is commonly called Kegani.

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How Is Hair Crab Eaten?

Hair Crab can be prepared in several ways.

Common methods include:

• Steamed Hair Crab
• Boiled Hair Crab
• Crab meat dishes
• Soups
• Crab rice
• Dishes using the rich internal organs

Fresh Hair Crab is often steamed or boiled with minimal seasoning so that its natural sweetness can be enjoyed.

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Nutritional Value

Like many crustaceans, Hair Crab meat is a good source of protein.

It may also provide nutrients such as:

• Protein
• B vitamins
• Phosphorus
• Selenium
• Zinc
• Copper
• Various marine fatty acids

Exact nutritional content varies depending on body part, season, size, and cooking method.

The internal organs are flavorful, but they may also be relatively rich in fat, cholesterol, and sodium depending on preparation, so moderate consumption is advisable.

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How to Choose a Good Hair Crab

When selecting Hair Crab for food, several characteristics may help indicate freshness and quality.

Look for:

• A crab that feels heavy for its size
• Legs that are mostly intact
• A firm, hard shell
• No unpleasant rotten odor
• An overall solid and fresh appearance

Freshness criteria differ depending on whether the crab is live, chilled, or frozen.

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Why Is the Hair Crab an Important Fishery Resource?

Hair Crab is an economically important seafood species in parts of Korea, Japan, Russia, and other areas of the North Pacific.

In northern Japan especially, it is considered an important commercial crab species.

Because of its high market value, fisheries may regulate factors such as:

• Harvest season
• Minimum size
• Catch quantity
• Fishing areas

These management measures help prevent excessive harvest and support long-term population stability.

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Ecological Role

The Hair Crab is an intermediate consumer in benthic marine ecosystems.

It feeds on smaller animals and organic material while also serving as prey for larger predators.

A simplified food relationship can be represented as:

Small Benthic Animals and Organic Matter → Hair Crab → Large Fish and Octopuses

By feeding on benthic organisms and then becoming prey itself, the Hair Crab helps connect different levels of the marine food web.

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Interesting Facts About Hair Crabs

Hair Crabs have several fascinating characteristics.

First, as the name suggests, their bodies are covered with dense short hairs.

Second, they prefer cold northern waters rather than warm tropical seas.

Third, unlike long-legged Snow Crabs, Hair Crabs have a rounded body and thick, sturdy legs.

Fourth, they must molt repeatedly in order to grow.

Fifth, they do not hatch directly into miniature crabs but instead pass through several zoeal stages and a megalopa stage.

Sixth, females have a long reproductive cycle and may carry eggs for an extended period.

Seventh, although they are smaller than King Crabs, their sweet meat and rich internal organs make them highly valued as premium seafood.

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The Hair Crab, or Horsehair Crab (Erimacrus isenbeckii), is a cold-water crustacean found around the east coast of Korea, Japan, the Bering Sea, Alaska, and other parts of the North Pacific.

Its carapace and legs are covered with dense hairs and fine spines, giving it a rough and distinctive appearance.

Hair Crabs mainly live on sandy, muddy, or gravelly seafloors in cold marine environments.

They grow by molting and pass through the developmental stages:

Egg → Zoea Larva → Megalopa → Juvenile Crab → Adult

The species is also notable for its relatively slow reproductive cycle and long period of egg brooding.

In addition to its ecological role as both predator and prey on the seafloor, the Hair Crab is an important seafood resource.

Its sweet meat and rich, flavorful internal organs have made it especially popular in Korea and Japan.

With its hairy shell, compact body, cold-water lifestyle, slow reproductive cycle, and high culinary value, the Hair Crab is one of the most distinctive and fascinating edible crabs of the North Pacific.