Japanese spider crab

Japanese spider crab Introduction

Of the 60,000 species of crustaceans on Earth, Japanese spider crabs are the largest, spanning up to 12.5 feet from the tip of one front claw to the other. They’re also one of the world’s largest arthropods, animals with no backbone, external skeletons, and multiple-jointed appendages. In this crab’s case, those appendages are its 10 legs. Japanese spider crabs live on the Pacific side of Japan as far south as Taiwan and at chilly depths ranging from 164 feet to as low as 1,640 feet. (They spawn at the shallower end of that spectrum.) They thrive in temperatures of about 50 degrees. In these waters, their mottled orange-and-white bodies, cream-colored undersides, and spiny, oval carapaces blend in with the rocks on the ocean floor. Those round shells and long legs give Japanese spider crabs an arachnid-like look, hence their common name. These animals also have spines behind and in front of their short eye stalks. Males are larger than females and have larger chelipeds, the legs that hold their claws, though females have wider abdomens to hold their eggs. These slow-moving crabs don’t hunt, preferring to scavenge for dead animal or plant matter, though they may also eat live fish or invertebrates such as other crustaceans.

Keywords to learn

Scavenge: Search for and collect (anything usable) from discarded waste

About Me

Hey Kids, my name is Jace the Japanese spider crab and I am very happy to meet you. Learn more about me and my species @




Key Data

  • Order:
  • Lifespan:
    Up to 100 years.
  • Class:
  • Scientific Name:
    Macrocheira kaempferi.
  • Mass:
    42 pounds.
  • Length:
    12.5-foot leg span.
  • Region found:
  • Population Status:
    Not evaluated .
  • Current population trend:
  • Diet:
  • Sexual maturity:
    No data.


The Japanese spider crab may look like something from a 1950s sci-fi film, but Japanese spider crabs are gentle giants.


Now that you know more about the Japanese spider crab by learning the key data above, be sure also to check out the fun facts. When you are finished learning the facts, try answering the questions in the Q&A corner on the bottom right side of the page.



Download questions about the Japanese spider crab here: Japanese Spider Crab (answers are on this page)


Teachers. For more in depth work sheets on  crabs. Click on Kidskonnect Worksheets



Japanese spider crab Fun Facts for Kids

  • # 1. When you’re the biggest crab in the sea and you only have a few predators out there to worry about, who do you decide to eat? The answer is pretty much anything smaller than you. They’re not exactly hunters, but these crabs have been known to eat algae, kelp, mollusks, slow-moving invertebrates, and the dead bodies of any creatures that happen to be floating around. 
  • # 2. This species is part of a group known as decorator crabs which adorn their shells with sponges or anemones for camouflage. Juvenile Japanese spider crabs will do this, but with few predators at the depths in which they live, adults of this species don’t have to dress to impress.
  • # 3. Japanese spider crabs migrate to the shallower end of their depth range during mating season, which lasts from January until April. 
  • # 4. Fertilization is internal, with the male inserting a spermatophore, or sperm packet, into the female as their abdomens press together. The female’s abdomen, also called the apron, is where she carries the fertilized eggs.
  • # 5. These enormous animals start out tiny—females produce more than a million eggs that are about .03 inches each. Not many will survive to hatch. h, but those that do will emerge after about 10 days and get no parental care.

Q&A Corner

# 1. What region does the Japanese spider crab live in?


# 2. What is the average lifespan of the Japanese spider crab?


# 3. What is the diet of the Japanese spider crab?


# 4. When is Japanese spider crab mating season?


# 5. How big are Japanese spider crab babies after they hatch?


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