Which crab is invasive in Europe and North America?

European green crab and Chinese mitten crab

Crabs Challenge – A 10-Question Trivia Quiz

Every year, tens of millions of red crabs march across Christmas Island to the sea, and the crabs challenge begins with that migration. Meet the Japanese spider crab with legs spanning nearly four meters, coconut crabs that climb palms and hermit crabs that trade shells in neat lines.

Start Crabs Challenge

🎯 Daily Trivia Challenge • 🧠 10 Questions • ⏱️ 150 Seconds

Question 1 / 10 Time: 150s

Migration
Where do millions of red crabs migrate each year?
Largest
Which crab has the largest leg span?
Coconut
Which is the largest land invertebrate?
Hermit
Why do hermit crabs use shells?
Sideways
Why do many crabs walk sideways?
Molt
How do crabs grow?
Fiddler
What is special about male fiddler crabs?
Blood
Which animal's blue blood is used to test medicines, though it is not a true crab?
Invasive
Which crab is invasive in Europe and North America?
Claws
What can crabs do with lost claws?

Explanations: answer key for all 10 questions

Q1: Where do millions of red crabs migrate each year?
Answer: Christmas Island
Roads are closed to protect them.
Q2: Which crab has the largest leg span?
Answer: Japanese spider crab
It can reach almost 4 meters.
Q3: Which is the largest land invertebrate?
Answer: Coconut crab
It can crack coconuts.
Q4: Why do hermit crabs use shells?
Answer: To protect their soft abdomens
They move to bigger shells as they grow.
Q5: Why do many crabs walk sideways?
Answer: Their leg joints bend that way
Some can walk forward.
Q6: How do crabs grow?
Answer: By molting their shells
They are soft for a while after.
Q7: What is special about male fiddler crabs?
Answer: One giant claw
They wave it to attract females.
Q8: Which animal's blue blood is used to test medicines, though it is not a true crab?
Answer: Horseshoe crab
It is more closely related to spiders.
Q9: Which crab is invasive in Europe and North America?
Answer: European green crab and Chinese mitten crab
They damage habitats and fisheries.
Q10: What can crabs do with lost claws?
Answer: Regrow them
It takes several molts.

Crabs Challenge – Armored Walkers

Crabs are crustaceans with a hard exoskeleton, ten legs and usually a pair of claws. There are over 7,000 species living in oceans, freshwater and on land, from tiny pea crabs to the Japanese spider crab.

Crabs grow by molting their shells, and many can regrow lost limbs. Hermit crabs borrow empty snail shells, fiddler crabs wave giant claws and coconut crabs climb trees. Many crabs walk sideways because of how their legs are jointed.

On Christmas Island, tens of millions of red crabs migrate to the sea to breed each year. Crabs are important in food webs and fisheries, but some, like the green crab and Chinese mitten crab, have become harmful invaders.

What This Quiz Teaches

Ocean fans and students will enjoy these questions.

Where red crabs migrate
Which crab is largest
Why hermit crabs need shells
How crabs grow
Which crabs are invasive

Did You Know?

Crabs can breathe through gills on land if moist.
Decorator crabs wear sponges.
Pea crabs live inside shellfish.
Some crabs live in trees.
Snow crabs live in cold seas.