Giant Japanese Spider Crab Facts

Giant Japanese Spider Crab Facts.

Giant spider crab
Giant spider crab. Image credit: Ruth Hartnup cc2.0

What would you do if you saw a spider with legs over 10 feet long from tip to tip? (That’s longer than your bed.) You’d probably run off screaming at the top of your lungs. Thank goodness no such spider exists, but a crab does and appropriately so, it’s called the giant Japanese spider crab.

It’s Giant, Alright


The Japanese spider crab gets its name from its eight legs, each so long that a pair can span up to 13 feet from tip to tip. That’s very long considering its body can grow only up to 15 inches wide – just a little over a foot.

No wonder the scientific name of the Japanese spider crab is Macrocheira kampfaeri. ‘Macrocheira’ comes from two Greek words – ‘makros’ meaning ‘big’ or ‘long’ and ‘cheir’ meaning ‘hands’ or ‘arms’. Together, they mean ‘long-armed’. Also, in Japanese, this crab is called taka-ashi-gani which translates to ‘tall legs crab’.

The Japanese spider crab can weigh up to 44 pounds – that’s about as heavy as a 6-year old child! It is not only the largest crab or the largest crustacean but it also holds the title for the largest arthropod. In case you’re wondering what an arthropod is, arthropods are animals with segmented bodies, jointed legs and visible, outer skeletons that look like armor. Other examples of arthropods include all insects, spiders, centipedes, lobsters and shrimps.

How Big Is The Largest Japanese Spider Crab?

Crabzilla in Sea Life Scheveningen. Image credit: Pvt pauline GFDL v1.2

Just how big can the Japanese spider crab get? Currently, the record holder is ‘Crabzilla’, whose legs measure 12 feet long from tip to tip. He was caught in 2009 and has been on display at the Sea Life Scheveningen in the Netherlands since 2010.

Another Japanese spider crab held at Sea Life Blackpool in the UK named ‘Big Daddy’ has legs that measure 10.2 feet across.

In 2011, a Japanese spider crab measuring 10 feet across was caught in Suraga Bay near Tokyo. It was named ‘Crab Kong’ and is believed to one day surpass the size of Crabzilla.

The Japanese spider crabs that are usually caught by fishermen, though, measure just around 3 feet across.

Giant Spider Crab Molting

Japanese giant spider crab exoskeleton
Japanese giant spider crab exoskeleton. Image credit: Darren Foreman cc2.0

The crab has an exoskeleton that protects 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. It sheds its exoskeleton as it grows – like a snake shedding its skin. A new soft skeleton develops beneath the old exoskeleton. Once it sheds its old one the new one is expanded by pumping in sea water and then it hardens. This gives the crab room to grow and also provides it with protection.

Lurking In The Depths

Giant Japanese spider crab
Image credit: James Emery cc2.0

Apart from a few aquariums around the world, you won’t be able to see Japanese spider crabs. That’s because they live in the ocean from depths of 160 feet to 2,000 feet. Normally, they are found at depths between 400 and 900 feet.

As their name, implies, they are only found in Japan, and only off the coasts that face the Pacific Ocean. They are especially abundant off the southern coasts of Honshu Island, the largest island in Japan.

Watch Out For That Claw

Image credit: Lycaon (Hans Hillewaert) GFDL v1.2

Apart from having eight legs, the Japanese spider crab has two arms, each arm ending in a claw, just like in other crabs, with male crabs having larger claws than female crabs. Its claws are known to be strong, able to grab items quickly, even human fingers, and apply enough force to cause serious injury. Ouch!

What to Eat?

Giant Spider crabs (Macrocheira kaempferi) at the Kaiyukan Aquarium in Osaka, Japan. Image credit: Chris Gladis (MShades) from Kyoto, Japan cc2.0

The Japanese spider crab isn’t a picky eater. In fact, it eats pretty much anything that it stumbles across, whether shellfish that they can pry open with their strong claws, dead fish, plants that grow on the ocean floor and even algae. Some say they even eat the bodies of dead sailors lying on the sea bed. They are more scavengers than hunters, after all.

Long Live the Giant Crab!

Giant Japanese spider crab1
Image credit: Christian Kadluba cc2.0

Often, with animals, the larger it is, the longer it lives. Just take a look at the elephant, which can live over 70 years, and the mouse, which only lives up to 2 years on average.

With crabs, the rule is the same. The pea crab, one of the smallest crabs, lives only 2 to 3 years. The Alaskan king crab can live for 10 to 20 years. The coconut crab, the largest land crab, can live for up to 60 years. And the Japanese spider crab? Scientists believe it has a lifespan of 50 to 100 years, making it one of the longest-lived crabs around.

Are Those Plankton?

Photomontage of planktonic organisms. Image credit: Kils GFDL v1.2

Do you know how baby crabs look like? In case you don’t, crab larvae look like tiny, transparent shrimp. At least, most of them do.

The breeding season for the Japanese spider crab takes place during the spring. During this time, they go much deeper. After mating, the female lays eggs and carries them around until they hatch. After hatching, the larvae have to go through three stages, molting or shedding their outer skeletons each time, until finally, they look like their parents but still smaller, of course. This can take up to 72 days, depending on the temperature of the water. Like other crabs, they will keep on molting as they grow until they reach their full, giant size.

Bring On The Decoration

Sponge Decorator Crabs
Sponge Decorator Crabs. Image credit: Richard Ling CC BY-NC-ND 2.0

Japanese spider crabs belong to the group of crabs called ‘decorator crabs’. These crabs are so named because they pick up objects in their environment and cover their shells with them as camouflage or protection. Japanese spider crabs share this habit, as well. They pick up sponges and kelp to keep themselves hidden. After all, although their legs are long, they are not very strong and in fact, can break easily. Many Japanese spider crabs have been caught with at least one leg missing and some as many as three. They can still survive but have a harder time doing so, of course.

Is It Endangered?

Japanese spider crab at Manila Ocean Park. Image credit: Tsarli (Charles Laigo) CC-BY-SA-3.0

Because the Japanese spider crab lives in the depths of the ocean, it is difficult to gather information about it. Its exact population is unknown. However, Japanese fishermen have reported that they are not catching as much as they used to and scientists fear that its population might have decreased significantly in the past 40 years. There are currently no conservation measures in place, simply a law in Japan that prohibits the catching of Japanese spider crabs from January to April when they are breeding. At other times of the year, they can be caught and are often served as a sought-after delicacy.

Japanese Spider Crabs are featured in the following book:
25 Deep Sea Creatures

The YouTube video playlist below contains videos about Japanese Spider Crabs. Details of the videos featured are underneath.

The Playlist:

  1. Japanese Spider Crabs by MrChubbyJB
  2. Giant Spider Crab Molting (time-Lapse) by MrPuppy07
  3. Crab With 9-Foot Claws Arrives at a UK Aquarium by GeoBeats News
  4. Strange Japanese Sea Creatures by NationalGeographic


To view the complete list of sources, click here.



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