Japanese Spider Crab – Facts That You Need To Know

Japanese Spider Crab is one of the most known creatures underwater by its abnormal characteristics!

It’s an arthropod that can live more than 100 years. Arthropods are animals like spiders, insects, and crabs that can be dangerous enough if we do not take care of them.

They are known for having long legs and bodies that are broken into somite. These types of animals tend to eat diverse kind of things, but the Japanese spider crabs are omnivores, they eat a wide variety of plants and animals as well.

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How Do Japanese Spider Crab Look Like?

One of their most striking characteristics is the orange and spiky body they have, known as the biggest arthropod by the scientists.

Its real name is Macrocheira Kampfaeri, which means “long-armed” and in Japan, it is known as “taka-ashi-gani” which means “tall legs crab”.

It has eight legs, but sometimes they can lose them to marine predators and to nets which are left by human predators. However, these spiders have the ability to grow new legs to replace broken ones when they molt.

Living Location & Distribution 

Japanese spider crabs tend to live in the Pacific Ocean near Japan; they can be as deep as 700-1,000 feet or more. They are commonly placed in holes deep in the ocean that’s why it is not that easy for fishermen to find.

The Japanese spider crab can be located to the Pacific sides of the Japanese islands, Kyushu and Konshu. These crabs can also be found in Easter Taiwan. Which is pretty rare.

If you want to see or catch one of these you better head to Sagami, Suruga, and Tosa bays, they are often found there.

Biogeographic Regions: Palearctic (Native)

Despite that, there are situations where they can be found as shallow as 50 meters which are only 130 feet deep.

In these situations, you have to be careful enough to avoid any lesion.

Morphology: They Can Grow Up to 12 Feet Long

As you must know, its name comes from its eight legs, each of them is so long that a pair can span up to 13 feet easily. However, its body can grow up to 15 inches wide.

The Japanese spider crab is the largest known living arthropod that can weigh up to 44 pounds. Despite it has a huge body and long legs, these tend to break off easily.

When stretched apart, adult specimens can be nearly 4 meters long from one tip of their claw-bearing leg to the other. However, the well-calcified carapace is only around 37 centimeters long.

The carapace stays the same throughout the adulthood, but the chelipeds and walking legs increase in length as the crab ages.

The carapace of the Japanese crab is sub-circular and pear-shaped. It’s narrower towards the head. The females have wider carapace compared to the male. Females have smaller abdomens than males.

Range mass: 16 to 20 kg.

Range length: 3.7 m.

Average length: 3 m.

Trophic Strategy: They Can Eat Anything 

As mentioned earlier, this spider crab is an omnivore scavenger. It eats plants and animals found on the seafloor, including dead fishes and shellfish as well.

The larger species generally do not hunt. They are mostly scavengers, they crawl along and pick at the dead decaying matter. They will occasionally eat living kelp and algae.

Their movements are somewhat slow however they will not miss the opportunity to hunt for small marine invertebrates that they can catch easily.

Many scientists report that these crabs are known to pry open mollusks at any moment of the day.

Animal Foods: fish; carrion; aquatic crustaceans; other marine invertebrates.

Plant Foods: algae; macroalgae.

They Can Live For Over A Century

Despite different kind of crabs that can live between eight and thirty years, the Japanese spider crab can live for at least a century or even longer which makes it an extraordinary sea animal.

However, it is said, the older it gets, the bigger it becomes. So, reading about how long they can last, we know it can get so much bigger.

Researches have demonstrated that one of the largest crabs ever caught alive was only forty years old.


The exoskeleton’s crab has one incredible advantage that is protecting it from larger predators such as octopuses.

It can also blend into the rocky ocean floor and adorn its shell with sponges and other animals, providing itself with a great camouflage.

These crabs are like snakes, they shed their exoskeleton as it grows and a new soft skeleton develops beneath the old exoskeleton. Once it sheds its old one, the new one is expanded by pumping in seawater and then it hardens.

Associations & Behaviors

The Japanese crab is not an active predator. It is mainly a scavenger that walks along the seafloor searching for the dead and decaying matter. These are also well-protected creatures.

Nearly all spider crabs will decorate their carapaces with sponges and other items but the Japanese spider crab won’t. The reason behind this behavior is that they have very fewer predators. That’s why they don’t need any camouflage. 

In The Beginning, They Cannot Be Seen 

Females carry the eggs around attached to their tummy until they hatch as tiny, legless larvae that float in the ocean as plankton.

These plankton crab larvae float around and grow slowly over the course of around 70 days before they actually begin to look like anything.

Their Claws Can Cause Injuries

Although the legs of the Japanese spider crab are very spindly, they're also quite muscular. Despite that, they can move quickly to kill their prey when needed. Thanks to the long legs they have, right?

Their claws are also strong and large enough to pry open mussels and clams in order to get at the creature inside.


Not much known about their method for communication. These are solitary creatures and often seen hunting for food alone. They are not active predators and that’s why their senses are not as acute as those that hunt. 


Some Interesting Questions Japanese Spider Crab

Q1. Can they survive after losing their legs?

Their legs are pretty vulnerable and can be broken very easily. However, they can survive after losing one of them for its power to regenerate the legs on their own.

Q2. Can these animals be eaten? 

There are still some people that call for them in parts of Japan and other Asian countries, so they are sold as a delicacy in some restaurants.

Q3. Are they endangered?

Their population is still unknown. However, Japanese fishermen have reported that they are not catching as much as they used to and the scientists fear that spider crab’s population might have decreased significantly in the last years.

Q4. Have they been caught in other countries?

No. All of them have been caught around Japan, but some of these creatures are in UK aquariums. Such as; the Japanese spider crab called ‘Big Daddy’ which has legs that measure 10.2 feet across.

Q5. Which one has been the biggest?

Currently, the record holder is ‘Crabzilla,’ whose legs measure 12 feet long. He was caught in 2009 and has been on display at the Sea Life Scheveningen in the Netherlands since 2010.

Q6. What is the most expensive crab?

Snow crab


Despite they live in the deep ocean, there are situations where they can be found near the surface that’s why it’s important to know the characteristics of these types of arthropods.

As we could see, although it’s a big crab spider, it can be eaten as a delicacy in restaurants. The Japanese spider crab has existed for many years and despite it can cause injuries, they are the favorite animals of Japanese people since long time ago.

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Last Updated on October 9th, 2020

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