Atlantic Horseshoe Crab: a two-minute wildlife lesson

Crabs and Shells · day 1 of 7

Five facts

1. Despite its name, the horseshoe crab is not a crab at all. Its closest relatives are spiders and scorpions.
2. It has nine eyes: two big ones on the sides of its shell, five small ones on top and two more underneath, close to its mouth.
3. Its blood carries oxygen with copper instead of iron. Pale inside the body, it turns dark blue when it meets the air.
4. A female buries her eggs in beach sand, laying from 15,000 to 64,000 of them. The bigger she is, the more eggs she lays.
5. Called a living fossil, the horseshoe crab has changed little in 445 million years, since long before the dinosaurs.

The quiz

1. Which animals are horseshoe crabs most closely related to?

• Lobsters and shrimps
• Spiders and scorpions (correct)
• Snails and clams
• Starfish and sea urchins

They are not crustaceans; their closest kin are spiders and scorpions.

2. How many eyes does a horseshoe crab have?

• Two
• Four
• Six
• Nine (correct)

Two large eyes, five on top of the shell and two underneath make nine.

3. What colour does horseshoe crab blood turn in the air?

• Dark blue (correct)
• Bright red
• Green
• Black

Its copper-based blood turns dark blue when it meets oxygen.

4. How many eggs can a female horseshoe crab lay?

• 2 to 4
• About 50
• 15,000 to 64,000 (correct)
• Exactly 300

A female lays from 15,000 to 64,000 eggs, depending on her size.

5. Why are horseshoe crabs called living fossils?

• They can live for 445 years
• They have changed little in 445 million years (correct)
• Their shells are made of stone
• They live only in caves

Their body shape has barely changed in 445 million years.

Same week

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