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Lanky legs, sponge fashion, and Japanese Spider Crabs

Writer: Jada Andersen
Jada Andersen
Jan 28, 2021
2 min read

Ever wondered what the largest crab in the world looks like? I certainly haven’t, but it’s as bizarre and freaky as you can imagine. This week we’re learning about the Japanese Spider Crab.



Quick Facts:

  • Scientific name: Macrocheira kaempferi

  • Geographic location: Japanese waters

  • Distinguishing feature: Long pincered legs

  • Conservation status: Population unknown, but threatened by overfishing


Japanese Spider Crabs are giants of the ocean floor. Their Japanese name (taka-ashi-gani) meaning ‘tall legs crab’ says it all. They have a leg span reaching up to 3.7 metres long claw to claw and weighing 20kg. Despite their huge size, strong claws, and tough exoskeleton, they’re soft (literally and metaphorically) on the inside. Spider Crabs are known to have a curious, and gentle disposition and do not threaten humans.


You’d think having long legs would be handy for walking and movement right? But in many cases it seems to be an inconvenience. Research has found that almost ¾ of the crabs found had limbs missing! They may be long, but they aren’t very strong. I suppose it’s bound to happen when you live to be 100 years old like they can.




Being unable to move quickly, they aren’t active predators but instead omnivorous scavengers. You’ll typically find them scraping algae off the ocean floor, or scraping molluscs from their shells. Whilst a hard exoskeleton helps protect them from predators, they tend to hide from predators by camouflaging their bodies with sponges and other animals.


Unfortunately, to grow they must shed this hard exterior and grow a new one. In the time it takes their new skeleton to harden, they are very vulnerable. Watch them camouflage and moult their skeletons in the clip below:



Whilst we don’t know much about their population size, overfishing is a major threat for Japanese Spider Crabs. Treated as a delicacy in Japan, fisherman use trawler nets to catch them in open water. To combat this, conservation laws prevent fishermen from catching them during the mating season (January to April). Japanese Spider Crabs can lay up to 1.5 million eggs each season, so laws like this are very effective for giving them enough space and time to reproduce.


Do you think Japanese Spider Crabs are scary? Or do you see them as Big Friendly Giants like me? Let me know in the comments!



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