All that variety comes from the same source: little animals called mollusks, with a mighty muscle called a mantle. I found out all about them from my friend Richelle Tanner , a scientist at Washington State University. She is very curious about the ocean and knows a lot about mollusks, a type of animal with a soft, moist body.
There are many kinds of mollusks: both on land and in the sea, with and without shells. Many move through life with just their soft bodies.
But some grow shells for protection, as a kind of traveling armor. The mantle forms the soft outer wall of their body. It absorbs salt and chemicals from the water around it.
It can be more difficult than you think. Have you ever been to the sea shore? If you have, you know that there are many shops along the shore that sell sea shells. Some of those stores are operated by women, so you could definitely say that "she sells sea shells by the sea shore " when referring to such women. The sea shells in shops by the sea shore can be beautiful. They come in all sorts of shapes, sizes, and colors.
There almost seems to be no end to the different kinds of sea shells you can find in these stores. But before you buy sea shells in a store, see what you can find on the beaches along the shore. A leisurely stroll along the beach will reveal thousands upon thousands of sea shells. Many of them are mere pieces and fragments of complete shells, but it's also possible to find the kinds of complete, beautiful sea shells you'd find in the stores along the shore.
So where do all these sea shells come from? Is there an undersea factory where mermaids and dolphins work hard to produce shells that they then send on the waves to shore? That's not it at all! The sea shells you see scattered along the shore are actually former homes! Homes for whom? Mollusks, of course! Sea shells are the left-behind external skeletons of mollusks. Mollusks are small invertebrate animals that usually have delicate, slimy bodies.
As mollusks grow, their shells protect their fragile bodies from the elements and predators that hunt them. As mollusks live their daily lives in the sea, they take in salts and chemicals from the water around them. As they process these materials, they secrete calcium carbonate , which hardens on the outside of their bodies and begins to form a hard outer shell. Although its shell is attached to it, it's not part of the living body of a mollusk. This is because the shell is formed from minerals, not mollusk cells.
As mollusks continue to excrete calcium carbonate , their shells continue to grow. When a mollusk dies, it leaves its shell behind for you to find along the sea shore. A mollusk 's shell material, called nacre , is mostly calcium. However, it also usually has an outer layer of hard scleroprotein , which is similar to human fingernails. There are many different types of mollusks. Moreover, different seas around the world offer mollusks all sorts of different diets. The different types of mollusks eating different types of diets explain the incredible variety of sea shells that can be seen on the shores of seas around the world.
For example, warm tropical waters provide more food sources for mollusks. As a result, tropical mollusks leave behind more colorful shells, since different foods provide different types of pigments. Cold-water mollusks, by comparison, tend to rely on more limited food supplies and leave behind shells that tend to be solid, darker colors. Join us in Wonderopolis tomorrow for a closer look inside what some might call a warm canine! She sells sea shells by the sea shore!
She sells…well, you get the idea! Check out the following activities with a friend or family member to learn even more about the fascinating world of sea shells:. Great question, Sasha! We're glad this Wonder sparked your curiosity! We encourage you to keep researching sea shells at your library and online!
Thanks for sharing your comment with us! We encourage you to submit your question to the Wonder Bank. All of the Wonder questions are submitted by Wonder Friends, just like you! Hey there, Jayy! Thank you for visiting us and sharing your thinking about sea shells. It made our day here in Wonderopolis! We hope to see you back again soon! We think many Wonder Friends were probably thinking the same thing before reading this Wonder, Madison. It's FUN when you learn something new visiting Wonderopolis, isn't it?
Thanks for shearing it guys!!!! We're glad you learned something new, Sasha! Thanks for stopping by Wonderopolis! Many of our Wonders come from curious Wonder Friends like you! We'd LOVE to hear some of them! Welcome back, Brandon! We're not sure how big shells can get. Evolution works in mysterious ways. Unlike seashells, turtle shells have living cells, blood vessels and nerves, including a large number of cells on the calcareous shell surface and scattered throughout its interior.
Bone cells that cover the surface and are dispersed throughout the shell secrete protein and mineral and more or less entomb themselves. The bone can grow and reshape continuously. And when a bone breaks, cells are activated to repair the damage. In fact, turtle shell grows from within just like leg bones in humans. Nutrients such as protein and calcium are supplied by blood vessels within the bone, not from outside of the bone tissue. Damaged seashells, on the other hand, use secretions of proteins and calcium from the mantle cells underneath the shell for repair.
Construction of both turtle shells and seashells share some fundamental mechanical properties. The currently accepted understanding of how shell forms is that the protein matrix of bone and seashell is secreted out of the cells. These proteins tend to bind calcium ions while guiding and directing calcification. Binding of calcium ions to the protein matrix enhances crystal formation according to precise hierarchical arrangements.
Exact details of this mechanism remain unclear in both turtles and seashells, but many proteins have been isolated that are known to play a role in shell formation. Seashells are self-repairing; they use the calcium carbonate secretions from their mantle tissue to fix any damage. Seashells vary so much because there are lots of different kinds of mollusks, eating many different types of diets. For example, mollusks in warm tropical waters have a wider variety food sources, so they get lots of different pigments, which results in more colorful shells.
On the other hand, mollusks who live in cold water have more limited food choices and tend to grow shells in more solid, dark colors. Before you take a bucket of shells from a beach, consider how important they are to the planet's ecosystems. Seashells may not be home to mollusks anymore, but they can still provide shelter for algae, armor for hermit crabs and nest-building materials for birds.
In most cases, it's not illegal to take seashells home the Mexican coastline, however, is considered an environmental reserve and it's illegal to remove any of its natural items , but if you don't want to cause harm to the planet, take photographs of them instead.
Claire is a writer and editor with 18 years' experience.
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