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Things You Always Wanted to Know About Shells



There are between 50,000 and 200,000 mollusk species alive in the world today. Estimates vary depending on who's guessing the number of undiscovered species!


Mollusk evolution began more than 500 million years ago, during the Cambrian period.

  Paleontologists use fossil shells to tell what the climate might have been like millions of years ago. Comparing fossil shells with their living relatives that only live in cold or warm climates can give some clues.

  Some oysters may shed over one million eggs in a season! Only about one out of every million of these oyster eggs lives to adulthood.

  Female cowries sit on top of their eggs to protect them from enemies!

  Some oysters alternate their gender: Male one year, female the next!

  A snail grows a bigger shell by getting calcium carbonate and other ingredients from the water and food it eats, then uses its fleshy mantle to add the new materials to the shell.

  When a hermit crab needs a bigger shell, it seeks a larger empty snail shell and moves in! Without a shell provided by a snail, it's naked!

  A young abalone that eats red seaweed produces a red shell! Color pigments from food can affect the shell color of some mollusks.

  Nudibranch is a mollusk family that doesn’t have a shell. Most are beautifully colored, too!

  Ninety-nine percent of all snail species have shell whorls that coil in a clockwise direction.

  Scallops have dozens of eyes. They help a scallop to see predators, so it will know when to swim away or clam-up!

  Carrier shells attach other shells or stones to their own shell for protection and camouflage.

  Shells have been used throughout history for art, jewelry, money, scientific study, buttons, ink, road gravel and chicken feed (for stronger egg shells!).

  Some cone shells obtain food by harpooning, paralyzing and eating fish!

  We hear the sound of the seashore inside large shells because the shell echoes surrounding sounds, jumbling and amplifying them.

  Many land snails can lift ten times their own weight up a vertical surface.

  Mr. Thomas Green of La Plata, Maryland, consumed 350 edible snails in eight and a half minutes.

  Mike Racz in Invercargill, New Zealand, opened 100 oysters in 2 minutes and 20 seconds.

  The ocean quahog Arctica islandica can live to be 220 years old!

  The deepsea bivalve Tindaria callistiformis grows only one-third of an inch (8.4mm) in 100 years!

  Boring clams can sink a ship! One of them, the misnamed Teredo Shipworm, earned its name by ruining wooden boats. It's actually a clam, and can bore through a six-inch thick plank of wood in less than one year!

  Many species of snails and clams breathe through a snorkel, or siphon, when they bury themselves in the mud or sand.

  Most mollusks are capable of making pearls when foreign substances enter their shells! They coat the foreign substance with shelly material.

  It takes about two years to grow a pearl. Some clams can grow pearls as big as golf balls in ten years!

A Snail's Pace | The Extremes

Facts compiled by John Caldeira. Some facts are generalizations,
and there may be exceptions.