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"The Beautiful Poison of our Marine Ecosystems"
Classification:
Kingdom: Animalia
Phylum: Echinodermata
Class: Asteroidea
Order: Valcatida
Family: Acanthasteridae
Genus: Acanthaster
Species: Acanthaster planci
Biological Description: Acanthaster planci, most commonly known as the crown-of-thorns starfish (COTS), resides among the largest sea stars on the planet, next to the sunflower star (Pycnopodia helianthoides), genus Thromidia, and Evasterias echinosoma. The image above is an unusual coloration of the organism, whereas, normal coloration is dull and brownish spikes projected from the grey body. Adult A. planci can grow between 25 to 35 cm in diameter (Moran 1986), and branches out numerous spikes all over its body as adulthood is reached.
The picture on the left is an organic molecule called plancitoxin I. This toxin is potentially lethal to humans and is found in the venom. The venom from the spikes also contains PLA2s, which are some of the enzymes also found in snake venom that is very toxic to predators. The venom from the starfish has a stable pH range of 3-10, and it acts similar to behavior of jellyfish toxins that change hemolytic activity, which is defined as the breakdown of red blood cells (Lee C. and others 2013). Venom also consists of saponins, which are known to cause foaming and inflammation to infected tissues in humans. The combination of these organic substances in the venom gives the starfish an advantage in anti-predator behavior by providing most predators a distaste for A. planci.
The abundance of COTS and its behavior have been well documented over the last 30 years in marine biology and invertebrate biology. Like most species of starfish, Acanthaster planci can regenerate arms and missing body parts when they become damaged. Unlike normal starfish that have five arms, the crown of thorns starfish can have up to twenty-one arms. These starfish feed by protruding their stomachs out on coral, dead coral, algae, and soft corals. The major predators of the crown of thorns include the trumpet triton (Charonia tritonis), wrasse (Family Labridae), triggerfish (Rhinecanthus aculeatus), and pufferfish (Family Tetraodontidae) that normally keep the starfish populations under control (Khaled Bin Sultan Living Oceans Foundation 2014). Even though these are the major predators of the starfish, they are not the only predators of A. planci, and A. planci is not only subject to prey by these predators (Moran 1986).
Distribution: Acanthaster planci is located in tropical Indian and western Pacific Oceans east to Panama and portions of the Gulf of California (Moran 1986). Local distribution of the starfish are in the protected areas of the reef (Moran 1986).
A. planci can be found where there is an abundance of plankton because the larvae feed on them. Sewage runoffs are a breeding ground for plankton, and thus, also a breeding ground for Acanthaster planci (Khaled Bin Sultan Living Oceans Foundation 2014). When the larvae mature, they head to deep water to find corals that they feast upon. A. planci is also found abundantly when there is overfishing of predators, in addition to sewage runoff. The predators are a key factor to where and when outbreaks of COTS occur because they control both larval and adult stages. In areas of the world where human activity is restricted, defined as no-take zones and reserves, researchers have been counting populations densities of COTS; most particularly in the GBR (Great Barrier Reef). There are little populations of the crown-of-thorns starfish in MPAs (marine protected areas), suggesting that fish predators are in abundance in these areas with little or no human activity of overfishing occurs (Sweatman 2008).
This has led to efforts to try to control outbreaks of COTS, which have been unsuccessful. The most efficient and common method to try to control the outbreaks is by injecting each individual COTS with sodium bisulphate, but the process is very time-consuming and only works when divers can see the starfish. Other smaller efforts include capture, routing of sewage pipes to new runoffs, and increasing areas of no-take zones. Increasing the levels of predators has been avoided as much as possible because the long term effects are poorly understood (Moran 1986). Most biological control studies that aim to stop outbreaks of any kind of species have failed to work and create other problems. Current research aims to find chemicals and pathogens that will affect only COTS and not cause biochemical harm to other organisms in the Bathypelagic zone and deeper parts of the ocean.
Interesting Features and Observations: The crown-of-thorns starfish spends almost 45% of its time feeding (De’ath and Moran 1998). Motion increases as the depth of the ocean increases and has the same correlation with the size of the starfish, respectively (De’ath and Moran 1998). More than 50% of the starfish stay hidden for 94.7% of their feeding time on corals, where they spend 89.2% of that time feeding (De’ath and Moran 1998). The lack of food will alter the starfish’s behavior by triggering the onset of stress and disease in high density populations and will cause the starfish to die out when coral fauna becomes scarce (De’ath and Moran 1998). Normal crown-of-thorns starfish behavior is to eat in a group and, consequently, most of these starfish will die when COTS eat up nearby coral reef populations. This is a natural response in the event that a crown-of-thorns starfish exhausts all of the nearby food. It is uncertain if genes are activated to accommodate this behavior or if it is an environmental stress response.
Another interesting feature of the crown-of-thorns starfish is the use of venom, which is produced inside the thorns, to hoard off predators. Figure 1 shows inflammation that has occurred when a person was stung by COTS. Blisters, swelling, and a foreign calcified object entered in areas that were ruptured in the skin. An experiment by Aniya and others (1998) was done to discover the potency of the venom. When injected into rats at full dose, all of the rats died. At 50% potency, all of the rats survived, with a decreased function of cytochrome P450 and microsomal GSH S-transferase (Aniya Y. and others 1998). Interestingly, these results have sparked scientists’ interests because these particular enzymes play a key role in human xenobiotic metabolic pathway and inflammation regarding cellular defense against toxins introduced into the body, respectively. The findings indicate that the poisons released from the starfish’s arms can be very harmful and deadly to humans in full potency or dosage. The findings at half dosage, however, are unique because the effects found in the rats could be used as potential desirable traits in treating human drug over-dosage. No studies to date have significant evidence on this and further research is being done to test for validity.
There are some odd, interesting observations about the sensitive environment that will kill A. planci than what other starfish are limited to. Individual COTS that are not able to find refuge from high tide events are more likely to suffer significant damage and even death if they
cannot find a suitable spot to feed because the starfish’s powers of adhesion decline with age (De’ath and Moran 1998). The starfish are also limited to the oxygen content in the water in the sense that they will die when placed in freshwater due to the lack of oxygen (Khaled Bin Sultan Living Oceans Foundation 2014). Bases are also relatively toxic to COTS as well. As previously mentioned in containment strategies, when sodium bisulphate is injected into the organism, it will kill the starfish due to the acidic properties of the compound, leaving the rest of the environment unharmed. This chemical has led scientists to the discovery of a new toxin. Recent research by Rivera-Posada and others (2011) have found a new promising toxin that will not just kill the starfish when injected, it will also spread to other starfish in a very gruesome manner and will destroy individuals within 24 hours of injection. Injecting COTS with TCBS (thiosulfate-citrate-bile-sucrose agar) will cause “discoloration, ulcerations, loss of body turgor, accumulation of colourless mucus on many spines, and loss of spines” (Rivera-Posada and others 2011). Fig. 2 shows how warm water temperature variation will affect the time required to kill 5 COTS. The study found many other unpleasant side effects, but most importantly, TCBS is transmittable to only A. planci without sending any other pathogens into the marine environment. Fig. 3 illustrates the image taken during the experiment of the disease transmissible effectiveness to other COTS.
COTS reproduces fast and in large, overwhelming numbers. Due to sewage run-off, COTS’s larvae are able to live longer and survive in massive quantities into adulthood. Females release up to 1010 eggs over the course of their lifetime. This fact has crowned the crown-of-thorns starfish as the most fertile invertebrate in the world (Khaled Bin Sultan Living Oceans Foundation 2014).
This statement is due to the correlation of high fecundity and a long larval stage that results in massive outbreaks of the organism.
Unique Phylogenetic Traits and Taxonomy only to Acanthaster planci: Unlike many organisms, there are limited genetic differences in peripheral populations and considerable gene flow among Acanthaster Planci populations over the entire world (John Benzie 1999). A feature like this can lead to extraordinary behavior that make it difficult to organize the starfish taxonomy together. Acanthaster planci and other asteroid species have similar larval stages that they are nearly impossible to decipher from. This creates difficulties for knowledge of the dispersal patterns and routes used by the COTS and how to fight infestations. Nina Yasuda and others (2006) made complete mtDNA sequences of A. planci and found codon usage and tRNA structure are very similar to the rare sister species, A. brevispinus. This finding shows a correlation with same characteristics between the two species, except for the significant differences in unassigned regions (Nina Yasuda and others 2006). This knowledge and sequence information will be useful in the research to find ways to contain the outbreak of A. planci without harming sister species of the phyla. These unknown areas in this particular field of study make COTS a very unique and interesting invertebrate.
Cited References
Aniya Y., Terukina R., Minamitake Y., and Shiohira S. 1998. Effect of the spine venom from the crown-of-thorns starfish, Acanthaster planci, on drug-metabolizing enzyme in rat liver. Journal of Toxicological Sciences; 23 (5): 419-424.
Australian Museum. Crown of Thorns Starfish Threaten the Great Barrier Reef. Online video clip. Youtube. Youtube, 22 Oct. 2014. Ret. 24 Nov. 2015.
Benzie J. 1999. Major genetic differences between crown-of-thorns starfish (Acanthaster Planci) populations in the Indian and Pacific Oceans. Evolution; 53 (6): 1782-1795.
De’ath G. and Moran P.J. 1998. Factors affecting the behaviour of crown-of-thorns starfish (Acanthaster planci L.) on the Great Barrier Reef: 1: Patterns of activity. Journal of Experimental Marine and Ecology; 220: 83-106.
Fig. 1 and caption. Adler M., Kaul A., Jawad A. 2002. Foreign body synovitis induced by a crown-of-thorns starfish. Photograph. Rheumatology; 41: 230-237.
Fig. 2 and caption. Rivera-Posada J., Pratchett M., Cano-Gomez A., Arango-Gomez J., and Owens L. 2011. Injection of Acanthaster planci with thiosulfate-citrate-bile-sucrose agar (TCBS). I. Disease Introduction. Diseases of Aquatic Organisms; 97: 85-94.
Fig. 3 and caption. Rivera-Posada J., Pratchett M., Cano-Gomez A., Arango-Gomez J., and Owens L. 2011. Injection of Acanthaster planci with thiosulfate-citrate-bile-sucrose agar (TCBS). I. Disease Introduction. Diseases of Aquatic Organisms; 97: 85-94.
Khaled Bin Sultan Living Oceans Foundation. Deadly Starfish Eats Coral: Crown of Thorns Starfish (COTS) crisis. Online video clip. Youtube. Youtube, 16 Jan. 2014. Ret. 24 Nov. 2015.
Lee C., Tsai W., Hsieh H., and Hwang D. 2013. Hemolytic activity of venom from crown-of-thorns starfish Acanthaster planci spines. The Journal of Venomous Animals and Toxins Including Tropical Diseases; 19 (22).
Moran, P.J. 1986. The Acanthaster phenomenon. Oceanogr. Mar. Biol. Ann. Rev.24:379-480.
Rivera-Posada J., Pratchett M., Cano-Gomez A., Arango-Gomez J., and Owens L. 2011. Injection of Acanthaster planci with thiosulfate-citrate-bile-sucrose agar (TCBS). I. Disease Introduction. Diseases of Aquatic Organisms; 97: 85-94.
Sweatman H. 2008. No-take reserves protect coral reefs from predatory starfish. Current Biology; 18 (14): 598-599.
Yasuda N., Hamaguchi M., Sasaki M., Nagai S., Saba M., and Nadaoka K. 2006. Complete mitochondrial genome sequences for Crown-of-thorns starfish Acanthaster planci and Acanthaster brevispinus. BMC Genomics; 7 (17).
This page on the Google website was made by: Timothy Hackett
BIOL 364: Invertebrate Biology
Fall 2015
Term Project and Paper
For more information on Acanthaster planci, please visit the following video links:
Deadly Starfish Eats Coral: Crown of Thorns Starfish (COTS) crisis - This is a link to a video by the Khaled bin Sultan Living Oceans Foundation. This video gives more information on the crown of thorns and is one of my references to my website. The ownership and rights to this video belongs to the Khaled bin Sultan Living Oceans Foundation and I take no credit in the making, ownership, endorsement, or any legal rights of the video.
Crown of Thorns Starfish Threaten the Great Barrier Reef - Here is another video by the Australian Museum. This video shows the ongoing research to contain the crown of thorns starfish. One of the methods shown in the video is injecting each individual starfish with sodium bisulfate. This method is very time consuming and other methods to contain the starfish are needed. The ownership and rights to this video belong to the Australian Museum and I take no credit in the making, ownership, endorsement, or any legal rights of the video.
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