Where Do Seashells Come From?

Learn why seashells are so important and how seashells are made

Seashells along the beach conjure up images of tranquility and the sound of the waves crashing to the shore. Some beaches seem to be covered in seashells, while others have very few. As the seashells may have traveled long distances to reach their beachfront destination, I often wonder about their stories. How far did they travel? Where did they come from, and how long have they lived? Just as the waves will always roll ashore, seashells will always tumble on the sand—each day bringing new shells and new discoveries to those who are willing to look, listen and learn.

But—where do seashells come from and how are they made? Let’s dive in and explore the fascinating world of seashells.

What are seashells?

Seashells are body parts (the shell) of an animal (mostly mollusks). Seashells are made of calcium carbonate. When you see a seashell by the seashore, you are seeing the empty shell of an animal that has died. The body that used to live inside the shell, usually soft and fleshy, has died, decomposed or been eaten by a hungry ocean creature. Once the shell-living animal has died and the shell is emptied, the shell is then free to float and swirl around the ocean. A seashell can travel thousands of miles to the shore and be thousands of years old when discovered. You have probably noticed that some seashells look perfect, while others look broken or destroyed; this is due to the power of waves in the ocean. 

What animals live in seashells?

Shells found at ocean beaches were most likely inhabited by mollusks. Some of the mollusks have bivalve shells—two pieces that open and close—like clams, scallops, mussels and oysters. Other mollusks that have shells include snails (gastropods) scaphopods (or tusk shells), polyplacophorans (or chitons) and some cephalopods (such as nautilus). Shells are the homes of mollusks, a place to hide, a built-in shelter and their protective exoskeleton. 

How old are seashells?

You are probably familiar with the crustaceans (lobsters, crabs) that shed their shells and then grow new, bigger ones. As the crustaceans grow their inner bodies, their outer shells must be shed (molting) in order to grow a new and bigger shell to accommodate their new size. 

Unlike crustaceans, mollusks keep their shells and grow or expand them while they are intact or on their fleshy body. They keep the same shells throughout their lives. This is kind of like living in your house while building add-ons and extensions. If you look closely at a seashell, you can see these growth rings—similar to the growth rings on a tree trunk. This growth pattern allows scientists to determine the age of seashells. Pretty amazing, right! 

Seashells continue to grow throughout the lives of the creatures inhabiting them, which can be a long time. Ocean quahogs are among the longest-living marine organisms in the world. The ocean quahog is a species of edible clam, a marine bivalve mollusk. Ocean quahogs live in the Atlantic and can live more than 400 years old. At 507 years of age, Ming the clam broke the Guinness World Record as the oldest animal in the world. Ming the clam was dredged off the coast of Iceland in 2006. Ming was born in 1499 and died in 2006—that age was calculated by counting annual growth lines in the shell.

ocean quahog clam

What are some important uses of seashells?

  • A new home: Hermit crabs scour the beach to look for a new home or shell. They have exoskeletons like other crustaceans but rely on other animals’ shells for additional support. Every time the hermit crab molts (or sheds its exoskeleton to grow), it must find a new, bigger shell.
  • Toothpaste: Did you know that humans have been brushing their teeth with seashells for thousands of years? This began with the ancient Greeks, who crushed oyster shells into toothpaste as a cleaning abrasive. For this reason, some toothpaste brands still add calcium carbonate to their products.
  • Musical instruments: I am sure you have heard or seen conch shell “trumpets” where someone holds an empty conch shell up to their lips, blows in it and makes a very loud sound. Seashells have been used as musical instruments for thousands of years. The oldest-known musical instrument from a shell was discovered in a French museum. This 17,000-year-old conch shell, modified to be played like a horn, was determined to be  the oldest known wind instrument of its type.
  • Medicine: The cone snail is a highly venomous sea snail which produces an extremely deadly toxin. When scientists were working to develop the antivenom for the toxin, they discovered the snail had properties that could be used for medicines that are made up of compounds that can be adapted as pharmaceuticals to treat chronic pain, diabetes and more.

Leave Seashells at the Beach

When you see a seashell by the seashore—leave it there! Unless you’re a hermit crab looking for a new home, please don’t take the seashells off the beach. You know the saying—leave only footprints, take only pictures. This applies to seashells on the seashore as well. 

Shell harvesting can increase shoreline erosion. And the removal of shells from beaches could damage ecosystems and endanger organisms that rely on shells for their survival.

How YOU Can Help

You can help us at Ocean Conservancy keep our seashell-covered beaches trash free. Let’s make sure that when a hermit crab is looking for a new home, it can easily find a shell (and not a tin can)! 

From plankton to whales, animals throughout the ocean are finding their homes polluted by plastics. Millions of volunteers from more than 173 countries have picked up 384 million pieces of trash since the start of Ocean Conservancy’s International Coastal Cleanup® in 1985, all the while recording what they find and helping inform research and legislation across the world. Every bottle, every straw, every piece of trash you clean up can lead to a cleaner, healthier ocean.

No matter where you are, you can help ocean creatures enjoy a trash free home. Ready to #SeatheChange? Find out how you can join Ocean Conservancy’s International Coastal Cleanup.

Our work is focused on solving some of the greatest threats facing our ocean today. We bring people, science and policy together to champion innovative solutions and fight for a sustainable ocean.
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