During my summer vacation in 2019 at Lady Elliot Island, off the coast of Queensland, Australia, I overheard two visitors talking about the Crown of Thorns Starfish (COTS) feeding habits. They were discussing the starfish and coral reefs, so I decided to jump in and share what I knew.
I explained that starfish are not poisonous to humans, but COTS sharp spines can cause injury If touched. I also explained how their feeding on coral polyps can harm coral reefs, a big problem for marine life.
This conversation inspired me to write a post about what do Crown of Thorns Starfish eat? I think it’s important for people to understand this topic to better appreciate how delicate coral reef ecosystems are. So let’s answer the question with a quick response.
Crown of Thorns Starfish food contains hard corals such as staghorn and table corals, coral polyps, tiny creatures like sea anemones, and jellyfish. An adult Crown of Thorns Starfish can eat up to 10 square meters of coral in one year.
They are coral reef predators who use a special way of eating called external digestion. The starfish pushes its stomach out of its body, covers the coral, and releases digestive juices to break it down. The starfish then absorbs the nutrients, leaving behind white, dead coral. While they help control coral growth, having too many of them can cause major damage to the reef.
What Do Baby Crown of Thorns Starfish Eat?
Baby Crown of Thorns Starfish diet is different food than adults. When they are larvae (tiny, floating creatures), they feed on plankton. Plankton includes very small plants and animals that drift in the ocean.
As they grow into juveniles (young starfish), they start eating algae. Algae are tiny, plant-like organisms found on rocks and other surfaces underwater. This stage of their life is important for their development. Once they become adults, they switch to eating coral.
Read about 10 Kinds of Starfish You Can Find In California Waters( A Fascinating Look)
Crown of Thorns Starfish Feeding Mechanism Explained.
The Crown of Thorns Starfish feeding pattern is very unique. Their feeding behavior differs from most animals’ eating. Let me explain you in easy way.
1. Finding Coral
The Crown of Thorns Starfish uses its many tiny tube-like feet on the underside of its arms to crawl over coral reefs and find food. These feet help it stick to surfaces and move smoothly. The starfish also has simple eyes at the tips of its arms to sense light and dark, helping it locate coral. Once it finds coral, it positions itself to start its unique way of eating
2. Pushing Out Stomach
When the Crown of Thorns Starfish finds coral, it pushes its stomach out through its mouth. The stomach spreads over the coral and releases special juices that turn the coral into liquid. This helps the starfish absorb the food easily.
3. Absorbing Food
Once the coral is broken down into liquid, the Crown of Thorns Starfish pulls its stomach back into its body, absorbing the nutrients. This process can take several hours, depending on how large the coral piece is. An adult Crown of Thorns Starfish can consume up to 6 square meters of coral in a year, significantly impacting the reef ecosystem.
Unlike most starfish that have five arms, the Crown of Thorns Starfish can have up to 21 arms, giving it more reach to find and feed on coral. This makes it one of the most efficient coral predators in the ocean.
What Eats Crown of Thorns Starfish? Top 5 Predators of King of Thorns Starfish.
Despite their venomous spines, Crown of Thorns Sea Star have natural predators that help control their population: These natural predators include:
1. Giant Triton Snails (Charonia tritonis)
Also known as trumpet shells or triton’s trumpets, these large snails are one of the starfish’s main predators. They use their strong, pointed radula (a tongue-like organ) to drill into the starfish and feed on its tissue.
2. Harlequin Shrimp (Hymenocera picta)
Sometimes called painted shrimp or clown shrimp, these small but striking creatures specialize in eating the soft tube feet of the Crown of Thorns Starfish, making it vulnerable.
3. Reef Fish
Fish like pufferfish (Tetraodontidae), triggerfish (Balistidae), and Napoleon wrasse (Cheilinus undulatus) are known to prey on young or small Crown of Thorns Starfish.
4. Crabs
Some species of crabs, particularly larger reef-dwelling varieties, may feed on parts of injured or young starfish.
5. Sea Anemones
Some sea anemones have been observed preying on small Crown of Thorns Starfish by trapping them with their tentacles.
Humans also act as indirect predators by physically removing the starfish during outbreaks to protect coral reefs.
Why Are Crown of Thorns Starfish a Problem?
Crown of Thorns Starfish (Acanthaster planci) are large predators in coral reef ecosystems, feeding on coral tissues. They are coral-eating starfish and a natural part of these ecosystems, their populations can grow too quickly under certain conditions, leading to outbreaks that cause extensive damage to coral reefs. Understanding what triggers these outbreaks and their effects on reefs is vital for managing and protecting coral ecosystems.
Biology & Behavior of the Crown of Thorns Starfish
COTS are typically 25–35 cm (10–14 inches) in diameter, but can sometimes grow up to 40 cm (16 inches). They have a central disc surrounded by long, spiny arms, which contain tube feet used for movement and feeding. COTS are dioecious, meaning they have separate sexes, and reproduce by releasing eggs and sperm into the water. A single female can release millions of eggs during spawning. The eggs develop into free-swimming larvae that settle on the reef and transform into adult starfish.
Factors Driving Crown of Thorns Starfish Outbreaks
In healthy reef environments, the growth of COTS is controlled by their natural predators, like the napoleon wrasse and some species of snails. However, certain factors can increase the COTS population, leading to outbreaks that damage coral reefs. The main factors contributing to these outbreaks include:
1. Increased Nutrient Levels
Excess nutrients, especially nitrogen and phosphorus from agricultural runoff, sewage, and industrial waste, can promote the growth of plankton. Plankton is an important food source for COTS larvae, and when there is an abundance of plankton, more COTS larvae survive, leading to population growth.
Studies show that areas with higher nutrient levels often experience larger COTS populations. For example, areas with high nitrogen levels in the Great Barrier Reef saw up to 300% more COTS than areas with lower nutrient levels.
2. Loss of Natural Predators
The removal of predators due to overfishing or habitat destruction can cause COTS populations to grow unchecked. Key predators of COTS, such as the napoleon wrasse and Charonia snails, are often reduced in number, allowing COTS to proliferate. In some regions, the loss of these predators has directly led to outbreaks. Without these natural checks, COTS numbers can increase rapidly.
3. Climate Change & Ocean Warming:
Rising sea temperatures are known to affect marine species, and COTS is no exception. Warmer waters can increase the growth and reproduction rates of COTS. Studies of the Great Barrier Reef have shown that outbreaks tend to occur more frequently during periods of warmer water temperatures. Additionally, stressed corals are more vulnerable to predation by COTS, further exacerbating the impact of outbreaks.
4. Coastal Development & Pollution
Human activities such as coastal development and pollution can harm coral reefs and contribute to COTS outbreaks. Increased sedimentation, chemical runoff, and nutrient pollution can weaken reef health and disrupt the balance of marine life, making it easier for COTS to thrive. In areas with heavy coastal development, COTS outbreaks have been more common, as pollution creates favorable conditions for the starfish’s larvae.
The Impact of COTS Outbreaks on Coral Reefs
COTS are voracious feeders, consuming large amounts of coral tissue. They feed by extending their stomachs over coral polyps, digesting them externally. One adult COTS can consume up to 6 square meters of coral per year. When outbreaks occur, they can decimate entire coral reefs, leading to a loss of coral species and a reduction in biodiversity.
Quantifying the Impact
COTS outbreaks are responsible for around 40% of coral loss in some areas of the Great Barrier Reef. During an outbreak, COTS densities can reach over 1,000 individuals per hectare, compared to the normal population of 30–50 per hectare. This sharp increase in COTS numbers leads to significant coral damage, with some areas experiencing up to 90% coral loss during an outbreak.
Management & Control of Thorny Starfish Outbreak
Managing COTS outbreaks involves addressing the factors that promote their growth, such as nutrient pollution and loss of predators. Several methods are being used to control outbreaks and protect coral reefs, including:
- Manual Removal: Divers physically remove COTS from affected reefs. This method has been effective in some areas but is not a long-term solution due to the labor required and the potential for COTS to return.
- Restoring Natural Predators: Efforts to rebuild populations of COTS predators, such as the napoleon wrasse, are ongoing. By restoring these natural predators, it may be possible to control COTS numbers more effectively.
- Reducing Nutrient Runoff: Implementing better agricultural practices and reducing pollution can help lower nutrient levels in coastal waters, which in turn could reduce the availability of food for COTS larvae.
- Research and Monitoring: Continued monitoring of COTS populations and reef health is essential for the early detection of outbreaks. Researchers use underwater surveys and satellite images to track COTS numbers and assess the impact on coral reefs, allowing for quicker intervention.
Once in 2016, while snorkeling in the Hawaiian Islands, my friend Tim and I saw a Crown of Thorns starfish. It was our first scuba trip there, and we were excited.
The Starfish with Spikes looked amazing but was covered in sharp, venomous spines. Crown of thorns starfish sting is very painful, We had to be very careful. I used my tripod to move it off the rocks and into our bucket gently. Then, we brought it to the shore to look at it more closely. Luckily, we didn’t get hurt. After checking it out, we put it back in the ocean safely.
This was a special moment and taught me to respect sea creatures.
When I visit beaches in Florida, like Siesta Beach or Panama City Beach, my kids sometimes ask, “Dad, are starfish poisonous?” I always tell them not to touch starfish or disturb them. It’s better to leave them in their home and enjoy watching them.
Also Read: How Do Starfish Breathe? 10 Secrets (Explained By A Marinebiologist)
10 Amazing Facts About Crown of Thorns Starfish
1. Size & Appearance
The Crown of Thorns Starfish can grow up to 40 cm (16 inches) across, with arms stretching 25–35 cm (10–14 inches). Their body is covered with sharp spines that can cause pain to humans if touched. The spines have toxins that can make handling them dangerous.
2. Fast Reproduction
Crown of Thorns Starfish can produce a lot of offspring. A single female can release up to 65 million eggs during one spawning event. This happens each year, and in some areas, they can spawn multiple times, which allows their numbers to grow quickly.
3. Feeding on Coral
These starfish are predators of coral. They feed on the soft tissue of hard coral species by extending their stomach outside of their body and digesting the coral externally. One adult COTS can eat up to 6 square meters of coral in a year, and during an outbreak, this damage can be extensive.
4. Where They Live
Crown of Thorns Starfish live mainly in coral reefs across the Indo-Pacific, from the Red Sea to the Great Barrier Reef. They thrive in shallow water, usually from 3 to 50 meters deep, where there is plenty of food for them and their larvae.
5. Larvae Diet
The larvae of the Crown of Thorns Starfish mainly feed on plankton, especially phytoplankton. The survival of larvae depends on the amount of plankton available. If there is a lot of plankton, the larvae are more likely to survive, which can lead to larger numbers of starfish.
6. Spines as Defense
The spines on the Crown of Thorns Starfish not only help protect them from predators but also contain venom. If a person is stung by one of these spines, it can cause painful swelling, but it is rarely deadly. The venom serves to keep away animals that might want to eat them.
7. Wide Range
These starfish can be found in many areas across the Indo-Pacific region, including the coasts of Australia, Indonesia, and the Philippines. They are also found around some islands in the Indian Ocean. Their range has expanded in recent years due to changes in the environment, such as more nutrients in the water.
8. Sensitive to Changes
Crown of Thorns Starfish are sensitive to changes in the environment. Warmer sea temperatures can help them grow and reproduce faster, which can lead to an increase in their numbers. Coral reefs that are already under stress are especially vulnerable to these starfish.
9. Long Lifespan
Crown of Thorns Starfish can live for 5 to 10 years in the wild. However, during outbreaks, their lifespan might be shorter because they run out of food (coral). Even though they can live for many years, the damage they cause to reefs during outbreaks can be long-lasting.
10. Natural Predators
In healthy coral reefs, some animals naturally control King of Thorns Starfish populations. These predators include the napoleon wrasse and certain types of snails. When these predators are removed due to overfishing, COTS populations can grow uncontrollably, leading to outbreaks.
Conclusion
I explained What do Crown of Thorns Starfish Eat? & how they eat coral and help keep the ocean balanced, Their sharp, venomous spines keep them safe, and they eat in a very unusual way by pushing out their stomachs.
Things like pollution, overfishing, and warmer oceans can cause these starfish to grow in numbers and damage reefs. By learning about them and protecting coral reefs, we can help the ocean stay healthy. Always remember to watch sea creatures without touching them and let them stay in their home.
FAQs(Frequently Asked Questions)
Where does the Crown of thorns starfish live?
The Crown of Thorns Starfish lives in tropical and subtropical coral reefs across the Indo-Pacific region, including the Great Barrier Reef, the Red Sea, and Southeast Asia. They prefer depths of 1 to 65 feet and hide in reef crevices during the day.
Tell me about the Crown of thorns starfish habitat.
The Crown of Thorns Starfish lives on coral reefs in warm tropical and subtropical waters. You can find them in places like the Great Barrier Reef, the Red Sea, and Southeast Asia. They usually stay in shallow water, about 1 to 65 feet deep, and hide in cracks during the day. Coral reefs give them food and a safe place to live.
Can you eat Crown of Thorns starfish?
No, Crown of Thorns Starfish are not safe to eat. Their spines contain venom that can cause severe pain, swelling, and other health issues if touched or ingested. Additionally, these starfish are vital for coral reef ecosystems, so it’s better to admire them in the ocean rather than consider them as food.
What is the lifespan of a crown-of-thorns starfish?
Crown of Thorns Starfish can live up to 8 years. They survive without food for 9 months but shrink when starved. They have sight and smell organs and move using tiny tube feet under their arms.
