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Creatures of the Deep: Shell Game

Biologist Gary Vermeij sees with his hands. By handling shells, he is able to "read" the biology and history of the mollusks that once inhabited them. Using his sense of touch, Vermeij can find clues to the shell's life and can distinguish between a fossil millions of years old and a modern-day snail shell. His work has led him to theorize about the parallel evolution of mollusks and their enemies, ideas that are forcing other scientists to reconsider the roles of predator and prey in evolution.

Curriculum Links
Activity: Seashore Jeopardy




natural selection
ocean life



In the style of the television program Jeopardy!, here are 10 "answers" from the category of "mollusks and arthropods." Use these clues to identify familiar sea creatures you might find on the beach. Remember to respond in the form of a question.


    A: This marine mollusk is a snail with a conical spiral shell found at the water's edge.

    Q: What is a periwinkle?


  1. This crustacean is a squatter, finding a home in the abandoned shell of a snail and moving from one shell to another for protection as it grows.

  2. As this mollusk grows, it moves to the foremost portion of its beautifol shell, sealing off the space vacated behind it. Each abandoned chamber then fills with air, giving the mollusk buoyancy.

  3. The ribbed shell of this creature is made of two hinged halves called valves. Its large muscle is a favorite of shellfish eaters.

  4. These abundant edible bivalve mollusks live in crowded beds; the mollusks anchor themselves to pilings or rocks in clumps.

  5. This sedentary marine crustacean permanently attaches itself in colonies to rocks, pilings, boats and some marine animals and secretes a calcareous (limestone) shell around its body.

  6. This bivalve marine mollusk lives buried in mud or sand. Its many species are especially valued as food. It feeds by collecting food particles from water passing through its gills.

  7. This gastropod (literally "stomach foot") with a coiled shell forms the largest class of mollusks; some species are great delicacies in French cuisine.

  8. This marine gastropod mollusk is hunted for its large, edible muscolar foot and the iridescent mother-of-pearl lining of its shell, used for buttons and jewelry.

  9. When a piece of grit gets between its shell and mantle, this animal can transform it into a valuable natural pearl.

  10. The long tail of this arthropod might look scary to some beachgoers who don't realize it is merely a rudder. If the animal flips over, it can stick its tail into the ground and right itself.

Correct "Questions":

  1. What is a hermit crab?

  2. What is a chambered nautilus?

  3. What is a scallop?

  4. What are mussels?

  5. What is a barnacle?

  6. What is a clam?

  7. What is a snail?

  8. What is an abalone?

  9. What is an oyster?

  10. What is a horseshoe crab?


  • Make up similar games of Jeopardy! about other forms of ocean life -- marine mammals, echinoderms, marine plants or coral -- and compete as teams.

  • Bring in shells and try to identify or match to similar shells by handling them blindfolded. Can you feel scars or ridges?

  • How does the evolution of mollusks and their predators parallel the arms race between the world's superpowers during the Cold War?

  • The shells of mollusks (phylum Mollusca) make great finds at the beach. When you find a shell at the seashore, remember that it was once part of a living creature. A shell can tell you a lot about the animal that once inhabited it. The shell of a mollusk is formed by the mantle, a thick flap of skin surrounding most of the animal's body. Cells in the mantle secrete calcium carbonate and other materials to make the shell (exoskeleton). Most mollusks live in the sea but some live on land. Some arthropods, especially from the class Crustacea, also have exoskeletons you might find on the beach.


Scientific American Frontiers
Fall 1990 to Spring 2000
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