7 Fascinating Marine Animals With Shells! See Pictures

Last updated on February 4th, 2022

A recent visit to the beach with my friends got me wondering about the smaller marine creatures, which we don’t usually consider to be an integral part of marine life.

Marine animals with shells

  • Crabs
  • Barnacles
  • Lobsters
  • Turtles
  • Shrimps
  • Prawns
  • Balanus

Being a teacher, I’m used to innocent but intriguing questions put forward by the youngsters. But what I found was that our knowledge of marine creatures is quite limited.

We discuss the conservation and protection of larger species like whales, walruses, and seals whenever we speak of marine animals. Moreover, we seem to have more knowledge about these animals.

However, when it comes to the crustaceans, arthropods, and mollusks that I see whenever going to the beach, I’ve come to realize that my knowledge of marine animals with shells is indeed limited.

So I went ahead and did some research to not only build up my knowledge base but to also share with those who seek an answer to a similar question I had.

Table of Contents

Here are seven marine animals with shells:

1. Crabs

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This marine creature is the most popular member of the crustacean family.

Crabs are arthropods with thick exoskeletons and it’s this exoskeleton that appears to us as shells.

People often make a common mistake when comparing crabs to other marine creatures with shells because they think crabs are mollusks.

But crabs don’t grow their exoskeleton since it doesn’t expand as they age. Instead, they need to shed their exoskeleton in a process called molting.

Unlike mollusks, the exoskeletons of crabs don’t grow along with its body and as a result of this, several species of crabs found across the globe will regularly move from one shell to another.

Amongst these, you must have heard about the hermit crab, however, the hermit crab isn’t an actual crab since it isn’t born with shells nor does it have a tough exoskeleton.

It’s categorized under crabs because it lives in a shell and periodically leaves its cover searching for a new one.

Hermit crabs are born without shells which makes their abdomen vulnerable to any predator attack which is why they need to locate an adequate shell size to protect their exoskeleton.

A unique feature of the hermit crab is that it often decorates the surface in which it lives to camouflage its ‘house’ and protect itself from predators.  

2. Barnacles

barnacles 28082021

Barnacles are another category of crustaceans that have shells. The shells of barnacles not only make them unique but also their ability to attach themselves to objects in large numbers.

Barnacles occur in colonies and can attach themselves to the hulls of ships, reefs, submerged rocks, buoys, and even whales.

If you see sharp and protruding objects that resemble seashells on submerged rocks on beaches, chances are that these will be barnacles.

These creatures release a powerful natural glue that helps them to adhere to any object.

Once the barnacles have attached themselves to an object, it’s nearly impossible to detach these marine critters.

The adhesive of the barnacles is like fast-curing cement which allows them to adhere to objects even underwater.

You can also find barnacles even in underwater volcanoes.

These unique aquatic creatures have shells that are made of calcium plates. Barnacles secrete the calcium to form the plates that completely encase it which creates a protective coating.

Of the six plates that cover the barnacle, four of the receptacles include a door-like opening. The front of the barnacle opens up to absorb moisture.

The coating forms a cone-like structure giving the barnacles their unique design.

If the barnacles adhere to reefs, they need to open and close the door according to the flow of the tide.

3. Lobsters

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Lobsters are invertebrates, and they have a tough exoskeleton, which forms the animal’s shell. 

Like crabs, lobsters also shed their shells, but the unique feature of lobsters is that they consume a significant amount of water when it’s time to molt, and this forces the shell open.

This consumption of water is also necessary because lobsters exhaust an extensive amount of energy to molt.

When lobsters are ready to shed their old exoskeleton and emerge with their unique shells, they’ll go into hiding to ensure that they’re not vulnerable to any nearby predators.

Another unique feature of the shell of lobsters is that it hardens as the lobster grows older. This means the frequency of shedding its shell decreases as it ages.

A young lobster will shed its shell more frequently compared to an older one. Moreover, an older lobster will have a more rigid surface compared to a younger one.

4. Turtles

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Another marine creature that has a shell wholly attached to its body is the turtle. The hard surface of the turtle not only acts as its shelter but also its defense mechanism.

A turtle will retreat into its shell if it feels threatened.

A unique fact about turtles is that, unlike tortoises, not all turtles can retract completely into their shell.

The turtle’s shell grows with the animal, and unlike other marine creatures, they don’t need to change it because the shell will continue to grow with the turtle throughout its life span.

Another fact about a turtle’s shell is that it’s made of fifty separate bones. Studies have shown that the turtle shell houses both the rib cage and the spine of the animal.

Hence, the surface isn’t just the animal’s defense mechanism; it’s integral to the turtle’s body. It protects the delicate internal organs of the turtle.

The turtle shell has nerve endings and bones necessary for the animal’s body to function.

Hence, unlike other marine creatures, a turtle will never shed its shell. The cover is a part of its body.

5. Shrimps

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Shrimps are decapod crustaceans that have elongated bodies with a thin shell covering them.

It would be best to be acquainted with this crustacean as shrimps are harvested and even caught for consumption.

Shrimp farming and fishing for shrimp in the wild is common in many parts of the world.

If you’ve observed a shrimp closely, you’ll find an outer shell that can be detached from its body like a lobster.

Shrimps too shed their shell or molt. Once they shed their shell, it tends to have a pinkish shade that’s easily distinguishable.

Additionally, shrimps shed their shell quite often. Specific types of shrimps shed their shells nearly once a week.

However, before shedding their shells, shrimps will look for a spot where they can hide since this molting process leaves them open to attacks from predators.

Shrimps are one of the most delicate marine creatures, even though they have an outer shell.

When shrimps are born, the shells of these creatures are pretty delicate and as they grow, their shell also becomes harder.

6. Prawns

prawns 28082021

Prawns, like crabs, also have a hard exoskeleton. Prawns are often found to have an orange-colored exoskeleton which is caused by the presence of a chemical called astaxanthin.

This chemical not only adds pigmentation but also helps the crustacean to camouflage. Prawns like shrimps shed their skin or molt.

However, prawns usually have a longer lifespan compared to shrimps. Prawns have a lifespan of nearly a year, and an adult prawn will shed its skin after one to one and a half months.

A prawn’s shell consists of almost five percent of its body weight. Hence, it would be best to be careful while shelling a prawn that there are no remnants left.

The exoskeleton or the shell of a prawn is indigestible. The three main chemicals found on the surface of a prawn are calcium, protein, and calcium carbonate.

It’s the calcium carbonate that gives the shell its toughness.

A fun fact about prawns is that it takes about ten to fifteen minutes to complete the molting process, and until then, it lies nearly motionless.

7. Balanus

balanus 28082021

Balanus is another category of marine creature that lives entirely inside its shell.

It belongs to the family of crustaceans, and it usually grows on bedrocks. Balanus is usually found nearly sixty meters below sea level, and you’ll find these in a colony of barnacles.

A balanus can grow from a size of five millimeters to ten centimeters and much like the barnacles, the balanus secretes a glue-like substance that helps it to adhere to any surface it finds itself.

The barnacle will survive entirely inside a stone-like shell, resembling a greyish or a whitish rock.

Like a barnacle, it has a six-layered conical-shaped cover that stays adhered to the rock.

The main component of the shell is calcium carbonate which gives it a strong structure.

The exterior of a balanus is waterproof and impermeable. This means even water cannot penetrate the Balanus shell.

But there is a small door on the surface of the balanus that helps them consume the plankton and dead organic material floating on the ocean floor.

Thus, the outer shell is a protective coating and both the ‘house’ of the balanus.

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