Sea Animals With Shells (+ Fun Facts)

You must have seen many adorable land animals taking your home in shells! But what about sea creatures? Yes, there are many sea animals with shells, in fact, more than land animals.

Examples of sea animals with shells include pistol crabs, clams, oysters, mussels, scallops, nautilus, and others. The majority of marine species have hard shells that protect their fragile bodies. Shells provide predator protection.

Few sea animals such as mollusks spend their entire lives in their shells. Others, like oysters, produce precious pearls in them!

Sea Animals With Shells

Pistol Shrimps

Sea Animals With Shells (+ Fun Facts)

Shrimps are the first animals on our list of sea animals with shells. The carapace refers to the top portion of their exoskeleton. The carapace extends slightly above the eyes to the area called the rostrum.

The rostrum is a rigid extension of the crab’s head and serves as a defensive and offensive tool. The entire exoskeleton protects the shrimp’s soft interior.

A very unique type of shrimp. This is a pistol Shrimps. As the name suggests, Pistol shrimps create bubbles by exhaling at high speeds. This produces a snapping sound like a pistol.

Pistol shrimps are commonly found in shallow seas of tropical and subtropical regions.

Fun Fact: The sound that pistol shrimps make is loud enough to break glass!


Sea Animals With Shells (+ Fun Facts)

Clams are sea creatures equipped with a shell core that is connected by two additional muscles. They belong to the group of mollusks known as bivalve mollusks, together with clams, oysters, and scallops.

To open or close their bipartite gills, clams’ contract or expand their accessory muscles. However, not all clams are shaped the same.

Some species, such as Paulorde clams, have triangular or oval-shaped shells. Its shell is bright white with orange or yellow markings and a blue tinge on the dorsal line on the inside. Its outer surface is mostly pale brown and yellow with black markings.

Others, like the razor clam, resemble old-fashioned razors. Their shells are parallel-sided and elongated. Razor clams often do not go up from the bottom because they are buried about 2 feet below the surface.

Fun fact: An interesting fact about clams is that they have a nervous system, heart, stomach, and kidneys.

Japanese Spider Crabs

As the name suggests, this scary-looking crustacean looks exactly like a spider at first glance. They resemble enormous spiders with their twelve-foot-long legs! Japanese spider crabs are the largest living arthropods and crustaceans.

This crab’s carapace width can increase to 16 inches. In order to defend themselves from stingrays and octopuses, among other predators, they have an armored exoskeleton. Its dark carapace blends well with the rocky sea floor and is excellent camouflage.

By coating their shells with sponges and other animals, Japanese spider crabs further deceive other creatures. It uses its tongue to mold these creatures before fastening them to its shell.

Over time, this creature becomes part of the shell. This action shields the entire body of the animal from intruders.

The Japanese spider crab also undergoes a 100-minute molting process, meaning its outer shell and other coverings are regularly shed. The molting process begins at the rear of the carapace and ends at the walking legs.

Fun fact: Japanese spider crabs can live over 100 years!


Sea Animals With Shells (+ Fun Facts)

Oysters are saltwater bivalve mollusks that are mostly known for their delicacy and stunning pearls. In some oyster species, the valves are irregular in shape and heavily calcified.

Oysters come in a type of varieties, and so do their shells. The shells of prickly or spiny oysters are covered in many spikes that jut out like thorns.

Saddle oysters or jingle shells have translucent, very thin paper-like shells. Their shell copies the contours of the object it is lying on. It is usually a large shell of another creature or rock.

The windowpane oyster, a type of saddle oyster, has capsicum shells that are used to make decorative items such as lampshades.

Pearl oysters are part of the feather oyster family. They produce beautiful pearls within their shells.

Fun Fact: Oysters are self-reproducing animals that can fertilize their own eggs.

American Lobsters

The American Lobster, which may be found along North America’s Atlantic coast, is prized by many. They are the heaviest arthropods and crustaceans in the world and weigh between one and nine pounds.

Like all other lobsters, American lobsters have a hard protective exoskeleton. They shed this exoskeleton as they grow. This makes them vulnerable during this period. Interestingly, many species change color during shedding.

American lobsters are divided into different species based on the color of their shell. An ingredient called crustacyanin gives blue lobsters their distinctive hue. They are the most common type.

Red, yellow, or orange, split, and white or albino are further types.

Rare lobster species are white lobsters or albinos. It is estimated that only one in 100 million is a white lobster.

Fun fact: American lobsters grow their entire lives!


Sea Animals With Shells (+ Fun Facts)

Just like other bivalve mollusks such as clams and oysters, mussels are eaten as a delicacy around the world.

Their shells are asymmetrical and elongated compared to other clams, which are more round or oval. Mussel shells have three layers and are often dark brown, black, or blue in color.

Muscles called adductors, which are powerful, connect the two halves of mussel shells. Shells protect the animal from predators and drought. They assist soft tissue by serving as a support.

Calcium carbonate is used to make the pearl muscles’ inner layer. White calcium carbonate crystals in the protein mixture make up the middle portion.

Additionally, the periostracum, an outer layer, is comprised of the protein conch. This layer protects the middle part of the mussels from being eroded by acid dissolution.

Fun fact: Mussels are one of the healthiest foods to add to your diet!


Krill are small crustacean creatures that are an important food source for many marine carnivores. Because of this, they are among the most important animals in aquatic ecosystems.

Its name comes from the Norwegian for “little fish fry”. Curlew lives up to six years and can grow up to 2.4 inches.

Like other crustaceans, krill have a mat-like exoskeleton or shell. The head, thorax, and other internal organs are shielded by the shell. Most kinds of krill have transparent outer shells.

A krill’s body contains unique, specially created bioluminescent organs. In other words, curls can produce light! Light is used by them for communication, camouflage, and counter-illumination.

Fun fact: Krill swarms may be spotted from space despite their microscopic size!


Nautilus are cephalopods, despite the fact that their hard shells give them the appearance of mollusks. They grows up to 10 inches in diameter.

They have the ability to completely retract and lock into their planar spiral shells. The opening of the shell is covered by a leather hood made of folded tentacles.

The shell of the Nautilus is made up of two layers. It has a shiny, prominent white inner layer. The outer layer is somewhat dull white.

The interior of the shell is the most stunning color of blue. Their shells can withstand pressure and only explode 800 meters below the surface.

Internally, the shells are divided into different chambers. The upper layer of their shell is black with irregular stripes. This helps them to blend into deeper waters.

The underside is almost entirely white, making it virtually invisible in brighter areas of the water.

Fun fact: The nautilus has about 90 tentacles, which it uses to detect compounds in the water that indicate either food or danger.


Sea Animals With Shells (+ Fun Facts)

Another bivalve mollusk used as a portion of fancy food; scallops are often mistaken for scalloped potatoes!

Scallops may move more freely than other bivalve mollusks because of their sleek shells. Additionally, their shells shield them from predators.

The right and left valves comprise the scallop’s two valves. Most scallops rest on their right valve. This makes it rounder than the left.

Unlike other scallops, scallops have a unique comb-like structure called the ctenolium on the posterior edge of the right valve. Most scallops lose this after maturity.

Like true oysters, scallops contain a single muscle inside their shells. Additionally, this muscle is much more developed in them than in oysters since they are aggressive swimmers.

These sea animals with shells can be found in oceans all throughout the world, but the Indo-Pacific region is where they are most prevalent.

Fun fact: Scallops have over 200 eyes around their gills!


Chitons are marine mollusks that live near the coast. They are elliptical in shape and use their large flat feet to cling to rocks and crawl along the ocean floor. The chitons range in size from the tip of a finger to as big as a human foot!

They may resemble snails, but their upper shell is really made up of eight different valves. These valves or shell plates overlap and overlap slightly at the anterior and posterior edges. A muscular skirt known as the girdle surrounds these shell plates.

The chitin shell allows them to move freely and bend upwards during locomotion. It also protects them from predators. If disturbed or uprooted by rocks, they roll into a ball like a wooden line.

Chiton’s shell valves come in many colors, patterns and textures. About 600 species of chitons are found in warm parts of the world.

Fun fact: There are over 1,000 living species of chitons!


Sea Animals With Shells (+ Fun Facts)

The last member of our list of sea animals with shells is the barnacle. Although different in appearance from others, barnacles are classified as crustaceans.

They are born as free-swimming larvae that resemble crustaceans. These are encrusters that attach themselves to living symbionts/substrates such as sea snakes, lobsters, whales and even other crustaceans.

The majority of typical acorn barnacles develop their shells directly on their substrate.

Free-living barnacles attach themselves using cement glands. These glands are part of the calcified plate. A ring of such plates surrounds the barnacle’s body.

Depending on the species, the plates are held together in a number of ways, even tightly fused.

Always in their shells, barnacles reach for food in the water using modified legs to pull plankton and detritus in. They spend most of their time huddled under boats, rocks, and other hard surfaces.

Fun fact: Barnacles eat with their legs!

Last words

As we’ve seen, sea animals with shells come in a wide variety of hues, forms, and dimensions. While some look dangerous and scary, others look beautiful with their translucent colors.

Some even produce precious materials like pearls. The most popular crustaceans and mollusks are eaten in many parts of the world.

We have covered all the important sea animals with shells on our list. If any are missing, let us know!

Thank you for reading. I hope I’ve helped you learn something new about sea animals with shells and update your wildlife knowledge in general.

If you liked this type of article, I’d like to recommend you a similar read: animals with scales

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