Giant Japanese Spider Crabs Can Grow Bigger Than People

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Meet the largest crab in the world. Weighing up to 40 pounds and reaching up to 18 feet from claw to claw, it can grow to triple the size of the average man!

The Japanese spider crab (Macrocheira kaempferi) is actually the largest known arthropod, a group which includes crustaceans, spiders, and insects. It’s usually found off the coast of Japan, where it’s called taka-ashi-gani, meaning “tall legs crags.”

Von Karl-Heinz Meurer via Wikimedia Commons

And that would be right. Their massive size is due mostly to their long, spider-like legs, which continue to grow as the crabs age. But despite their impressive length, their legs are actually quite weak and prone to getting ripped off by predators and fishing nets.

Not to worry though  — Japanese spider crabs are hardy creatures. Not only can they survive with a few missing legs, but they actually grow back during molting. And some reports say they might be able to live up to 100 years old.

Image via Wikimedia Commons

Their size makes these crabs downright terrifying, but researchers studying the species say they are quite gentle. Moreover, they are not active predators.


In fact, they’re usually just trying to keep to themselves. Their bumpy legs help them blend into the rocky ocean floor and they decorate their shells with sponges, kelp, and other animals to confuse predators like large octopuses.

Spider crabs aren’t great hunters either, probably because their long legs slow them down considerably. Instead, they stick to algae and small shellfish or scavenge for dead animals and plants along the bottom of the ocean. 


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