Are seashells living creatures, like corals or sponges? Or are they the remains of a dead creature, some ocean fish’s bones? Seashells are neither living nor dead creatures, they are something that certain sea animals have crafted to provide protection for themselves. They are not made up of living cells, but of proteins and minerals which have hardened to form these various shells. So what sea animals are responsible for crafting these protective coverings, and why do so many of them end up empty on the beaches?
Sea Creatures That Make Shells
Seashells are created by soft-bodied mollusks. There is a huge variety of animals that are classified as mollusks, and what shell they make depends greatly on the specific species. Mollusks are slimy, delicate invertebrates that do not have an internal skeletal system to support them, so they create external shells to protect them from harsh ocean elements and predators. These hard shells form and grow with the mollusk throughout their lives.
Examples of mollusks that form shells include gastropods like freshwater snails, conchs, cone snails, and limpets. These mollusks create univalve shells. This means that they come as just one piece with a single opening. Bivalve shells have two hinged shells and are created by cockles, clams, mussels, scallops, and oysters.
How a Seashell is Formed
A seashell is formed by a mollusk’s outermost layer of tissue called the mantle. The mantle is what connects the mollusk to its shell, and the mantle is what supports the continual growth of the shell as the mollusk grows. The shells themselves do not contain living cells but are made up of proteins and minerals.
Calcium carbonate is the main mineral found in seashells. Two crystals are formed in seashells, calcite, and aragonite. Calcite is a very common crystal that is found in chalk, limestone, marble, coral, and seashells. Aragonite is a different molecular arrangement of calcium carbonate found in the innermost layer of seashells.
A seashell grows with the mollusk throughout its life, expanding along the outermost edges of a shell, resulting in growth rings similar to that of a tree.
Layers of a Seashell
Seashells consist of three layers, outer, middle, and inner. The outer layer consists primarily of proteins and is commonly rough, spiked, and bumpy. Proteins in the middle layer cause the calcium carbonate to form crystals that create a very tough layer, which will be the mollusk’s greatest protection. The inner layer is the one connected to the mantle. This layer is smooth, and the proteins in the inner layer cause the calcium carbonate to form aragonite crystals. These crystals create the smooth iridescent layer commonly known as mother-of-pearl or nacre.
What Happens to Seashells
Mollusks keep their shells for the duration of their life. When they die, however, what happens to their shells? Mollusk shells will gradually weaken and break as they are exposed to the elements of the oceans after the mollusk dies. Eventually, they are washed up onto beaches and shores all over the world. This is why most shells you will find at the beach will be empty and oftentimes partially broken. Over longer periods of time, these shells will continue to break down unit they become particles of the sand.
What Creates the Color in Seashells?
The color of a shell is determined by the salts, chemicals, and nutrients of the ocean the mollusk takes in while it is forming the shell. Because tropical waters are rich in nutrients and minerals, mollusks are more likely to form colorful shells in warm waters. Mollusks who live in colder and harsher ocean environments are more likely to have plain brown, white, or tan shells.
Found a Shell with a Mollusk Still in It?
What should you do if you find a shell with a mollusk still in it? Leave it. In most places, mollusks are protected marine animals, and it is illegal to take a shell with a living creature away from the beach without a license. While you may have found a huge or stunning shell, if the mollusk still makes it their home, you’ll have to leave it be and look elsewhere.
Seashells are the homes of thousands of species of mollusks. They are formed as a protective covering for these sea creatures who otherwise would never have a chance of survival with their fragile and shapeless bodies. Seashells grow with a mollusk throughout their life, and the shape is determined by the species of mollusk making the shell. Feel free to collect empty shells for a stunning shell collection but leave inhabited shells alone on the beach you find them. Taking care of the marine and coastal environments is a privilege and a responsibility, but it can be a fun and interesting hobby as well.
