Crown-of-thorns starfish (COTS) are coral-eating starfish. The Great Barrier Reef, as well as other reefs in the Indo-Pacific region, are home to these spiky aquatic organisms.
Where did the crown-of-thorns starfish originate?
We have two crews of 10 to 12 divers out in the ocean all year, regardless of the weather, culling and removing crown-of-thorns starfish. They rotate 10 days on and four days off.
‘It feels like we’re at war at times, but we’re obviously winning; we’re witnessing coral regrowth and can see the difference.’
The crown-of-thorns starfish, which is native to the Indo-Pacific region, performs an important biological role in maintaining the reef’s diversity and delicate balance by feeding on the fastest-growing corals, allowing slower-growing coral species to form colonies. However, when the population of deadly starfish grows to epidemic proportions, it poses a serious threat to coral.
The first crown-of-thorns outbreak on the reef was documented in 1962, with further major outbreaks from 1978 to 1991, 1993 to 2005, and the current outbreak, which began in 2010, following.
Coral cover on measured reefs has decreased by roughly 50% over the last 30 years, according to study from the Australian Institute of Marine Science. Nearly half of the decline was caused by crown-of-thorns starfish. According to the study, if crown-of-thorns starfish predation had not happened during the preceding three decades, average coral cover would have increased.
Water quality drops substantially when huge amounts of nutrients from land are released into the reef, and if this happens during the starfish’s summer spawning season, conditions are ideal for the starfish to develop, grow, and survive at a much faster rate.
The Australian Government, the Great Barrier Reef Marine Park Authority, the Reef and Rainforest Research Centre, and the Association of Marine Park Tourism Operators joined forces under the Australian Government’s crown-of-thorns starfish control program to protect corals on high-value reefs from this and future outbreaks. Projects like the Game Changer case study are also addressing declining water quality.
Since its launch in 2011, the program has combed over 80 reefs and removed over 300,000 deadly coral predators.
More than $7 million has been allocated by the Australian government for two 20-meter control vessels, research and development, and the training and operation of diving teams.
‘It’s dangerous job, so proper training and control of diver tiredness is critical,’ Steve said.
‘On the control vessels, we have a policy that if a diver has been spiked more than twice, they are no longer allowed to dive.’
The invention of a single injection cull procedure by James Cook University was a big breakthrough for the program. To cull the creature, a little single injection causes an allergic reaction in the starfish, causing it to break apart and die within 24 hours.
To get the same result, divers had to take the starfish from its original place and inject it more than 20 times.
‘The starfish are unable to cope with the toxin and have broken up in the water, making the dive much faster and safer for the divers and the reef,’ Steve explained.
The new procedure is thought to have resulted in a two-and-a-half-fold boost in injection efficiency. The results have been spectacular, with 27 000 starfish removed in eight days at Arlington Reef, 9000 at Batt Reef, and 14 000 at Spitfire Reef near Cooktown.
The crown-of-thorns starfish control program’s astonishing achievement is a vital component of the Australian government’s overall strategic strategy to protecting the World Heritage-listed Great Barrier Reef.
Was the crown-of-thorns starfish introduced to Australia?
The Crown of Thorns Starfish, also known by its abbreviation COTS, is responsible for around 42 percent of coral destruction on Australia’s Great Barrier Reef.
In reality, coral reefs all across the world are being harmed by outbreaks of this marine pest. The Atlantic Ocean is the only place where epidemic sightings have been reported so far.
This coral-eating starfish poses a threat to Australia’s tourism and fishing businesses, as well as the World Heritage-listed Great Barrier Reef itself, on a local level in North Queensland.
We wanted to learn more about the Crown of Thorns Starfish because it is one of the greatest dangers to the Great Barrier Reef’s survival.
We were fortunate to meet with two local specialists, Col McKenzie from the Association of Marine Park Tourism Operators (AMPTO) and Sheriden Morris from the Reef and Rainforest Research Centre, who are both at the forefront of COTS research and management (RRRC).
- COTS have been there for millions of years, according to fossil evidence, but outbreaks have only been seen in the last 50 years or so.
- COTS are a normal element of the ecology, and they only become overabundant when the reef is out of balance and sick.
- COTS can play a beneficial role in a healthy reef by devouring some of the faster-growing corals and allowing the slower-growing corals to catch up and rebuild.
- COTS was initially discovered in the Ryukyu Islands off the coast of Japan in the 1950s.
- The first COTS outbreak in Australia was discovered on Green Island in 1962. In Australia, there have been three to four outbreaks so far.
- Triton’s trumpet, white spotted puffer fish, lined worm, harlequin shrimp, and two species of triggerfish are among the few predators found in the Crown of Thorns (yellowmargin triggerfish and titan triggerfish). Red emperors, spangled emperors, and parrotfish have all been reported to devour young COTS before they develop spikes.
- Between October and March, when water temperatures are at their greatest, COTS spawn on the Great Barrier Reef. COTS females release eggs into the water, which are fertilized by sperm released by neighboring males. COTS with large females can lay up to 65 million eggs every season.
- COTS begin their lives as planktonic larvae that float on top of the sea for weeks before settling at the ocean’s bottom. They are most vulnerable to predators while they are young, before their spiky spines have fully developed. They acquire spines around the age of a year and begin to feed on coral.
- COTS can reach a diameter of one metre and have up to 21 arms as adults. They recover an arm within six months if they lose one due to stress or injury.
- COTS spines are long and pointy, with a thin epidermis that contains the venom ‘plancitoxin.’ Both marine life and humans are poisoned by them.
- COTS consume by passing their stomach through their mouth and spreading it all over the coral’s surface with their tube feet. The meal is then digested externally.
- Scleractinian is nearly solely consumed by adult COTS. They can go for up to nine months without eating.
COTS outbreaks are a threat to the Great Barrier Reef’s future because they are occurring more frequently and there is insufficient time for coral to rebuild between outbreaks.
Although a 15-year interval between outbreaks is reasonable, additional environmental factors such as cyclones and coral bleaching are putting the Reef at risk.
Several variables, according to research, are contributing to the rising number of COTS outbreaks. Excess nutrients in the water as a result of fertilizers and sewage runoff from the land, as well as overfishing, which reduces the number of natural predators, are examples.
In 2012, the AMPTO launched a COTS Targeted Control Program to protect dive sites. Throughout the year, a crew of 22 divers works to destroy COTS in these locations by injecting them with bile salts.
While this technique may work for dive locations that are essential to tourism operators, it is clearly not possible for bigger areas (and, let’s not forget, the Great Barrier Reef runs for over 2300 kilometers).
The Reef and Rainforest Research Centre (RRRC) is pursuing a more holistic approach and investigating strategies to address Crown of Thorns Starfish outbreaks in the same manner as agricultural pests are dealt with.
What is the purpose of crown-of-thorns starfish?
The crown-of-thorns starfish is so named because its body and limbs are covered in spines. In life, these spines are somewhat flexible and are used for mobility as well as defense against predators.
How long have crown-of-thorns starfish been around?
Using starch-gel electrophoresis, Nishida and Lucas looked studied genetic diversity at 14 allozyme loci in ten A. planci population samples. The samples came from all across the Pacific, including the Ryukyu archipelago (four places), Micronesia (two locations), and the Great Barrier Reef, Fiji, Hawaii, and the Gulf of California (one location each). For comparison, ten A. brevispinus specimens from the Great Barrier Reef region were included. Between the A. brevispinus and A. planci populations, there was significant genetic divergence (D= 0.20 +/0.02). (D is genetic distance). Despite the enormous distances between them, genetic variations between geographic populations of A. planci were minimal (D = 0.03 +/0.00; Fsr = 0.07 + 0.02) (Fsr is standardized genetic variance for each polymorphic locus). The degree of genetic differentiation was found to be positively correlated with geographic distance, implying that genetic homogeneity among A. planci populations is attributable to gene flow via planktonic larval dispersion. The decrease in successful larval dispersal over vast distances is most likely the cause of the distance effect on genetic divergence. Because of the high level of macrogeographic homogeneity, large allele frequency differences across nearby populations separated by around 10 kilometers were discovered. The Hawaiian people were the most distinct from the rest of the world’s people. These data do not justify treating the morphologically different eastern Pacific Acanthaster as a separate species, A. ellisii. The lack of distinct alleles in the central (Hawaii) and eastern Pacific (Gulf of California) populations shows that they are descended from the western Pacific populations.
The genetic link between A. planci and A. brevispinus is discussed in greater depth in the page for the latter species. These are definitely related species, with A. planci, a specialized coral-feeding species, thought to have evolved from A. brevispinus, a less specialized soft-bottom dweller.
Benzie looked at allozyme loci variation in 20 A. planci populations across the Pacific and Indian Oceans in a large geographic survey. The most remarkable result was a clear divide between the populations of the Indian and Pacific Oceans. Those off the coast of northern Western Australia, on the other hand, had a strong Pacific connection. The patterns of variation within regions were consistent with isolation by distance, with the exception of the very strong relationship between southern Japanese populations and populations of the Great Barrier Reef. The trend of declining levels of successful larval dispersal over large distances is visible once more. Benzie claims that the split of populations in the Indian and Pacific Oceans began at least 1.6 million years ago and is likely due to climate and sea level changes.
Echinobase, a knowledge base for the echinoderm research community, has the genome of A. planci.
Do crown-of-thorns starfish cause coral bleaching?
Crown-of-thorns starfish outbreaks have wreaked havoc on the Great Barrier Reef’s several reefs since 1962. In the World Heritage Area, a fourth outbreak is now ongoing.
Crown-of-thorns starfish (also known as COTS) are coral-eating marine invertebrates. They’re found on reefs all around the Indo-Pacific, and when the conditions are right, they may spread like a plague, decimating hard coral communities.
After coral bleaching, crown-of-thorns starfish are a major driver of coral loss on the Great Barrier Reef, according to our research.
On the Reef, AIMS manages a large crown-of-thorns starfish monitoring program. Over a 15-year period, this long-term study found that epidemics start in the north and travel south, with ocean currents moving larvae between reefs.
The surveys also reveal that good reefs rebound after outbreaks, but it takes 10 to 20 years. However, reefs that are subjected to additional stresses, such as coral bleaching, cyclones, or poor water quality, take longer to recover, and the coral may not fully recover before the next round of breakouts.
What do crown-of-thorns starfish look like?
The crown-of-thorns starfish (Acanthaster planci) has a central disk from which its arms emerge, similar to other starfish. They have many soft arms (more than the usual five) that are covered in spines, which distinguishes them from other creatures. Their arms are also prehensile, allowing them to grasp objects. Crown-of-thorns starfish can grow up to 10-14 in (25-35 cm) in length and have more than 20 limbs when fully grown. They’re also available in a range of colors, including bluish-purple, red, gray, and green.
How cute are they?
The COTS (a coral predator) is more interesting and appealing than cute. Their brilliant colors, such as purple, gray, and green, as well as their spiky body, are fascinating to observe.
How do they communicate?
The method these organisms communicate is mostly unknown. A recent study, however, may give some illumination, as it was discovered that they communicate with one another through chemical release. COTS from different places, such as COTS from the Indo-Pacific region (which are a coral reef pest) and COTS from Japan, have been found to release the same compounds. When they are attacked by a predator, they appear to emit various proteins, but there is still a lot more to discover about these fascinating aquatic critters.
How big is a crown-of-thorns starfish?
The average adult crown-of-thorns starfish is 10-14 inches long (25-35 cm). The long and pointed spines on the sides of the starfish’s arms and upper (aboral) surface resemble thistles, and can have up to 23 arms. They resemble a crown, which gives the animal its name. The spines are solid, pointed, and may easily puncture through fragile surfaces, growing up to 0.13 ft (4 cm) long.
How did it get its name?
The venomous thorn-like spines that cover the upper surface of the crown-of-thorns starfish (coral reef eater) give it its name. These resemble the biblical crown of thorns in appearance.
Would they make a good pet?
They cannot be kept as pets because they dwell in the waters and contribute to the balance of their ecosystems. Crown-of-thorns starfish are predators that eat a variety of corals. They can only live in the deepest parts of the ocean, where they may feed on vast amounts of corals.
Kidadl Recommendation: Only purchase pets from a reliable provider. It is important that you conduct your own research as a potential pet owner before deciding on your pet of choice. Being a pet owner is extremely rewarding, but it also necessitates a significant amount of time, effort, and money. Check to see if the pet you’ve chosen is legal in your state and/or nation. You must never capture wild animals or harm their habitat. Please double-check that the pet you’re thinking about buying isn’t an endangered species, isn’t on the CITES list, and hasn’t been captured in the wild for the pet trade.
Did you know…
One of the most interesting crown-of-thorns starfish facts for kids is that they feed on their prey, coral reef, by ejecting their stomachs from their bodies and covering the corals!
Crown-of-thorns starfish are nocturnal and can eat 53.8-140 square feet (5-13 square meters) of coral in a single year. COTS are the primary cause of reef damage in Australia’s Great Barrier Reef.
The poison of the crown-of-thorns starfish contains saponin, a chemical component that is deadly to both humans and fish. The sting of a crown-of-thorns starfish can produce numbness, tingling, nausea, and agony across the body.
On the Great Barrier Reef, AIMS has a large COTS checking operation. This long-term study found that epidemics start in the north and move south over 15 years, with the ocean transporting larvae between reefs.
Why is the crown-of-thorns starfish a problem?
Coral-eating crown-of-thorns starfish can be an issue. Under extreme circumstances, this sea star can have outbreaks that cause huge coral reef devastation, threatening the vital coral cover. Coral reefs are crucial for many undersea animals, and they also help to reduce the intensity of the waves that pound our coasts.
Can a crown-of-thorns starfish kill a human?
Although the venom of crown-of-thorns starfish (coral reef eater fish) cannot kill humans, their spines do contain neurotoxic and starfish poison, which is harmful to both humans and marine life.
We’ve painstakingly crafted a variety of interesting family-friendly animal facts for you to explore at Kidadl! Learn more about the ground beetle and the American dagger moth, two more arthropods.
You can even color one of our crown-of-thorns starfish coloring sheets at home to keep yourself occupied.
What happened to the crown of thorns?
The thornless remnants are housed in the treasury of Notre-Dame Cathedral in Paris, where they survived a horrific fire that devastated the roof and spire of the church in April 2019.
How can the crown-of-thorns starfish be controlled?
As part of the Marine Park Authority’s Crown-of-thorns Starfish Strategic Management Framework, the Crown-of-thorns Starfish Control Program was formed in 2012 and provides a tactical reaction to outbreaks.
The method employs dedicated vessels with highly trained crews to hand cull starfish using bile salts or household vinegar as a deadly injection. The Crown-of-thorns Starfish Control Program also includes strategic surveillance and monitoring efforts. This ensures that culling efforts are focused on the areas that will provide the most benefit, that progress is tracked, and that pest control outcomes are maintained once they have been reached.
Supporting the environment and Reef communities
The Crown-of-thorns Starfish Control Program provides social and economic benefits to Australians in addition to environmental benefits for the Great Barrier Reef’s health. The program has been delivered in collaboration with the Reef tourism industry through the Association of Marine Park Tourism Operators since its inception (AMPTO). The reef is kept healthy in areas where local tourism firms send their national and international customers to experience the Great Barrier Reef through targeted crown-of-thorns starfish control. More than 100 people, mostly from Queensland, are trained and employed as part of the initiative.
Program growth and funding
At first, the program only had one or two dedicated ships. However, the outbreak that started in the northern management region in 2010 migrated south over time. The Crown-of-thorns Starfish Control Program received more money in 2018. In 2018-19, the program was able to expand from two to six vessels thanks to the additional funding. The expansion of the program allowed for the first time the deployment of crown-of-thorns starfish control vessels in the Marine Park’s far north and far south.
Five crown-of-thorns starfish control vessels have been deployed in the Marine Park’s northern, central, and southern management districts as of 2019-20. Control activities are deliberately tailored within each management region to focus on reefs of high ecological and economic value.
Since 2012, the Australian government has been funding the Crown-of-thorns Starfish Control Program. The Reef Trust Partnership (RTP) between the Great Barrier Reef Foundation (GBRF) and the Department of Agriculture, Water and the Environment provided funding for the Program in 2019-20. (DAWE). The GBRF and the DAWE have fully supported it through the RTP for 2020-22. The GBRF, the Great Barrier Reef Marine Park Authority (the Marine Park Authority), and the Reef and Rainforest Research Centre have formed a strategic collaboration to deliver the Program’s manual in-water control component (RRRC).
Are crown of thorns invasive?
- Purple sea urchins (Strongylocentortus purpuratus) are native to the United States’ Pacific Coast. Natural predators of the purple sea urchin, such as sea otters and sea stars, have declined in numbers (Pearse 2006). The resulting population explosion of purple sea urchins has ravaged kelp forests, which are important homes for many marine animals (Pearse 2006).
- Europe and North Africa are home to the European Green Crab (Carcinus maenas). The crab, which is found in the Americas, Australia, and South Africa, preys on a wide range of creatures but is especially damaging to bivalves (Colnar & Landis 2007).
Who eats crown-of-thorns starfish?
The gigantic triton snail, humphead Maori wrasse, starry puerfish, and titan trigger fish are all predators of adult crown-of-thorns starfish. Shrimp, crabs, and polychaete worms are all predators of immature starfish.