Last updated on February 5th, 2022
My recent visit to the Great Barrier Reef was an eye-opener for me. Not only was it a majestic sight, but it also made me realize that the Great Barrier Reef is an entire ecological system in its own right.
During my visit to the reef, I came to know that there are several animals that survive on these coral reefs, and it took me by surprise. This hard rock-like structure is food for some animals!
Animals that eat corals:
- Sea snails
- Sea slugs
My marine biologist friend told me that small animals hide within the corals, and fishes are often found eating the corals to get to these microorganisms.
These can be in the form of coral polyps or other similar creatures that hide within the reefs. Sometimes divers can even hear the crunching sound of fishes breaking off bits of corals and feeding on them. My friend mentioned that several animals eat corals, and some of these are as follows:
Here are 7 animals that eat living corals:
Sponges are aquatic creatures without tails that are known to eat almost anything.
You’ll often find sponges growing near coral reefs, and they’ll eat plankton, bacteria, virus, and any edible thing they find satisfying.
If a sponge lodges itself on a coral, then there’s a good chance that it can destroy it.
Sponges secrete an acidic substance that allows them to eat and pierce through the shells of oysters, clams, and corals.
Unlike other creatures, sponges don’t actively seek out corals as a source of nutrition. But if they get lodged on a coral reef, they’ll extract the food necessary for their survival.
The polyps inside the corals are rich in other nutrients like vitamins, proteins, and micronutrients.
This steady supply of nutrients can cause the sponges to become dependent on the corals for food supply, hence why they’ll start feeding on the corals.
It’s worth noting that each cell within a sponge needs to get its supply of food to maintain the functions of the body.
Therefore, easy access to adequate nutrition will make the sponge dependent on the coral for food.
A parrotfish has about 1000, sharp chisel-shaped teeth that allow it to cut into the tissue of corals.
It uses this technique to break open the shell of the coral so that it can reach the nutritious polyps parts inside.
This fish is often found around coral reefs feeding off the corals. But in reality, they eat the algae surrounding the corals as well.
Algae are rich in proteins, vitamins, and several micronutrients and attract hoards of parrotfish.
It will chew the polyp and the coral to get the algae. But these fishes can’t separate the algae from the corals.
Hence to eat the algae, the parrotfish often break bits of the coral which makes it appear as though the parrotfish is eating the coral.
The parrotfish teeth are incredibly sharp, and they can easily break through the sensitive corals to extract the algae and the polyps inside the corals.
The blue triggerfish is another category of fish that is found near coral reefs.
Triggerfish have long bodies covered by thick leathery skin. Their coloration varies depending on where they’re located. Some species look blackish while others appear yellowish.
These fishes also have sharp teeth which can latch onto corals to suck out the polyp from the inside.
However, unlike most fish, the triggerfish don’t use their mouth to suck up water.
It’s not entirely correct that a triggerfish will eat a coral-like parrotfish. Most marine biologists will tell you that it’s a mistaken notion because, unlike a parrotfish, a triggerfish won’t bite off the head of a coral.
Instead, you’ll find a triggerfish swimming around coral, looking for a suitable spot to latch onto.
Once it identifies the right spot, it’ll break open the coral with its strong teeth and suck out the polyps that form the insides of the coral.
Additionally, triggerfish attacks can prove to be dangerous for any coral reef. The primary reason for this is any growing coral depends on the polyps for nutrition.
When the triggerfishes remove the polyps from coral, it deprives the coral of its food source.
Moreover, the process of breaking open the coral destroys the structure of the coral as well as the reef. Thus, the attack of triggerfish can spell disaster for a coral reef, especially a growing one.
4. Crown-of-thorns Starfish
The crown-of-thorns starfish is another aquatic creature that preys on corals. These starfishes travel in colonies and are known for their spiky, disc-shaped bodies.
The crown-of-thorns starfish is the largest of its kind and is mainly found in the Indian Ocean and the Pacific Ocean.
The unique feature of crown-of-thorns starfish is due to their multiple arms that are very flexible to the point where they can twist, bend and glide over corals.
A coral is a living object, and despite its rock-like appearance, it grows by consuming algae known as zooxanthellae.
But when a crown-of-thorns starfish lodges onto a coral, it’ll destroy the entire coral and the polyps inside it.
This venomous creature is known to release digestive enzymes that can liquefy the corals which in turn allow it to absorb the nutrients from the coral tissue.
An adult crown-of-thorns starfish can grow up to 35 centimeters and have 21 arms.
It has been recorded that an adult crown-of-thorns starfish can consume up to 6 square meters of coral reef in a year.
5. Sea Snail
Snails don’t normally eat corals, but overfishing and climate change have brought a specific change in the feeding habits of snails.
Marine biologists have observed that snails have started eating corals, especially the older ones.
Certain coral-eating snails occur naturally, but their growth has always been kept in check with the help of predatory fishes.
But due to overfishing and shallow water fishing, the number of such fishes has reduced. Larger fishes like pufferfish that eat snails have declined due to overfishing,
Snails usually inhabit the coral reefs and eat the live corals to access the plankton and the microorganisms residing inside the reefs.
Although most snails eat dead animal and plant matter, certain sea snails can prove to be predatory, and they pose a danger to the coral reefs.
You’ll often find butterflyfish swimming around coral reefs and eating the heads of corals to access the polyps within them.
Butterflyfishes survive on coral polyps, plankton, and other microorganisms that inhabit a coral reef. Sometimes these microorganisms live in colonies inside the corals.
The butterflyfishes will then have to bite off the head of the corals to access these organisms. These microorganisms are the main diet of the butterflyfish.
7. Sea Slugs
Specific categories of sea slugs are known to eat the polyps living inside the coral reefs.
The Nudibranch, which belongs to the family of molluscs, is a sea slug that you’ll find inhabiting coral reefs.
These creatures are predators and survive on the polyps in living coral reefs. The Nudibranches are known to release a potent venom in the form of a toxic slime that softens the outer shell of corals.
This makes it easier for the sea slugs to access the polyps and the other microorganisms inside the corals.
Sea slugs can prove to be dangerous to coral reefs, especially when they travel in groups. The sea slugs can attack and destroy an entire coral reef.
These creatures aren’t very big, but the slime released by the sea slugs can travel for longer distances while being able to destroy the reefs.
Marine biologists often fear the attack of sea slugs on younger reefs as these creatures prefer the growing coral reefs as suitable feeding grounds.
Growing coral reefs have more polyps than the older ones, attracting predators and making them more vulnerable to sea slug attacks.
The animals that regularly consume living corals are mostly aquatic creatures, namely sponges, parrotfishes, triggerfishes, crown-of-thorns starfishes, sea snails, butterflyfishes, and sea slugs.