Atlantic Blue Crab: a two-minute wildlife lesson

Rivers and Coasts · day 7 of 7

Five facts

1. A blue crab is blue-green because alpha-crustacyanin holds onto a red pigment. Cooking breaks it down, and the crab turns bright orange-red.
2. A female blue crab can lay up to two million eggs in one spawning, yet she mates only once in her lifetime.
3. Blue crabs can grow a shell up to 23 cm wide.
4. After her one mating, a female blue crab stores the male's sperm for up to a year to fertilize several egg batches.
5. In Italy, where blue crabs have invaded, fishing groups say they have cost clam fisheries up to €100 million.

The quiz

1. What happens to a blue crab when it is cooked?

• It turns bright blue
• It turns white
• It turns bright orange-red (correct)
• It stays blue-green

Heat breaks down alpha-crustacyanin, leaving the red pigment, so the crab turns bright orange-red.

2. How many times does a female blue crab mate in her lifetime?

• Only once (correct)
• Twice
• Every year
• Ten times

She mates only once in her lifetime.

3. How wide can a blue crab's shell grow?

• About 2 cm
• About 60 cm
• About 1 m
• About 23 cm (correct)

A blue crab's shell can reach 23 cm across.

4. For how long can a female blue crab store the male's sperm?

• Up to a week
• Up to a year (correct)
• Up to a day
• Up to ten years

She stores the sperm for up to a year.

5. Which fishery do blue crabs hurt in Italy?

• Tuna fishing
• Oyster farming only
• Clam fishing (correct)
• Eel fishing

Fishing groups blame blue crabs for big losses in clam fisheries.

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