Pacific Oyster: a two-minute wildlife lesson

Crabs and Shells · day 2 of 7

Five facts

1. A Pacific oyster can switch between male and female from one year to the next, usually during the winter.
2. In one spawning, a female releases about 50 to 200 million eggs, which drift off into the water like a small cloud.
3. A baby oyster swims until it finds a good spot. Then it glues itself down for good, with cement made by a gland in its foot.
4. This oyster copes with water from −1.8 °C, just below freezing, all the way up to a warm 35 °C.
5. Before the Tokyo Olympics, 14 tonnes of these oysters had to be cleared off the rowing and canoeing equipment.

The quiz

1. What can a Pacific oyster change from year to year?

• Its colour
• Whether it is male or female (correct)
• The number of its shells
• Its home ocean

Its sex can change from one year to the next, usually in winter.

2. About how many eggs does a female release in one spawning?

• About 10
• About 1,000
• About 50,000
• 50 to 200 million (correct)

A female releases about 50 to 200 million eggs in a single spawning.

3. How does a young oyster attach itself to its new home?

• With cement from a gland in its foot (correct)
• With sticky threads it spins
• By digging into the sand
• By holding on with tiny claws

It glues itself down for good with cement from a gland in its foot.

4. What is the warmest water temperature this oyster can withstand?

• 15 °C
• 20 °C
• 35 °C (correct)
• 60 °C

It can withstand water from −1.8 °C up to 35 °C.

5. Where were 14 tonnes of Pacific oysters found before the Tokyo Olympics?

• Inside the swimming pool
• Under the athletes' village
• On the running track
• On the rowing and canoeing equipment (correct)

They had grown on the equipment for rowing and canoeing.

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