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Phylum Mollusca > Class Bivalvia
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For nature guides: introducing bivalves
updated Oct 2016

What are clams?
Clams and snails are close relatives! They belong to a group of animals called molluscs. Other molluscs include octopus, squids and cuttlefishes!


Clamming up!

  • Let's take a closer look at a clam! Clams have a two-part shell. The shell is made up of two valves, hence their scientific name bivalve! Now you know a scientific word too!

  • There is a hinge between the two valves. (Use a dead clam to show this). A strong adductor muscle keeps the two valves shut. Did you know that when we eat scallops, the part we eat is the adductor muscle and not the animal?

Clam shapes

  • Let's see how many different kinds of shapes of clams we can find. How big do you think the biggest clam can get? Introduce the Giant clam.

  • The shapes of clams tell us how they live. Can you guess from the shape of this clam how it lives?
    • Is it streamlined or chunky?
    • Is it smooth or ribbed?
    • Is it light or heavy?

  • Clams can do much more than you think! Here's some of the things they can do:
  • If you were a clam what would you eat? How would you feed? Explain how clams feed.
  • The next time you eat a clam, have a closer look at it. Try to find out more about how it lives and what it eats.

Clams are important to the ecosystem

  • Clams are part of the food chain. Can we think of some animals that might eat a clam? Some charismatic animals to highlight: otters, sting rays, moon snails.
Clams and you
We all love to eat clams!
  • What is your favourite clam?
    • Do you know where it comes from? How was it caught? Was it farmed?
    • Do you know what it eats? (Here is a good time to explain red tide and other harmful algal blooms, etc and thus why they shouldn't eat wild collected clams)

Clam myths to dispel

  • Can we open this clam to check for pearls? Although all molluscs can produce pearls, pearls used commercially come mostly from farmed and not wild bivalves. Please don't vandalise our wild clams in the vain hope of finding valuable pearls.

  • Giant clams DO NOT trap divers in their shells. More about this.

  • Abalones are not clams (Class Bivalvia), they are snails (Class Gastropoda).

  • Clams are sometimes NOT safe to eat. Explain red tide and other harmful algal blooms, etc and thus why we shouldn't eat wild collected clams.
Handling tips

Where to find clams? Many are stuck onto hard surfaces such as rocks, jetty pilings, sea walls. Often wedged in cracks and other cool wet spots. Some are tiny. Many clams dig into the sand or mud, others are attached to the undersides of small stones.

Be gentle! When overturning a rock to look at clams, be gentle so as not to crush animals under the rock, and plants living on top of the rock. Be sure to return the rock to exactly the way you found it, and ensure the visitors also learn that they should do this.

Don't disturb clams: Don't rip them off hard surfaces, or dig them up from the ground. Try to point out features without disturbing them.

Don't kill live clams! Don't force open living clams. Instead, use shells of dead clams (usually many can be found washed up on the high shore) to illustrate any stories or concepts you might have.
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