The crown of thorns is not like any other sea star, it is the second largest sea star in the world, and resides mainly in coral reefs around the Red Sea, Pacific Ocean, and Indian Ocean. It is a nocturnal sea star that travels alone. It keeps much distance between themselves and other sea stars of its species. It feeds mainly on living coral and can consume up to 6 meters of it a year. They are venomous and can cause great damage to our coral reefs.
II. Anatomy:
The crown of thorns, also known as the Acanthaster planci, can be grow up to 80 centimeters in diameter. Most sea stars have only 5 arms, but the crown of thorns can grow up to 21 arms that extend radially from the body. The arms are covered with venomous spines that can pierce through skin and some clothing with barely any pressure. They have tube feet, which are located underneath the arms, which allow the crown of thorns to move around and can help them to open food such as mollusks.
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III. Form and Function:
The crown of the thorns prey only on live coral, unlike any other sea star. Sea stars have two stomachs, the cardiac and the pyloric. They turn their cardiac stomach inside out through their mouth to cover the coral and then digest it with enzymes. The pyloric stomach is located inside the body and is what gets the partially digested food. It will eat everything up until the calcium carbonate skeleton. Their food is then digested and released from the anus. They reproduce, by what is called spawning. A female crown of thorns can reproduce up to 100 million eggs a year. Through their pores, they eject sperm and eggs into the water, which meet and then fertilize. Due to the fact that the crown of thorns is covered with many venomous spines, it does not have many enemies. They do have a few, such as the triton’s trumpet, painted-prawns, Napoleon wrasse, and the green triggerfish. Though they have a few predators, it does not affect the survival of the crown of thorns.
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IV. Impact on the World/Humanity:
The crown of thorns multiply quickly not only because they have few predators, but also because if dismembered, they can recreate another sea star from the severed limb. Since there are so many of them and because they eat only live coral, they are being blamed for the destruction of coral reefs. Although, some ecologists say that the crown of thorns are actually helping prevent over population and encouraging coral reef biodiversity. They say this because the crown of thorns eat the faster growing coral which prevents them from over powering the slower growing ones.
V. Journal Article Review:
This is article is mainly about how the crown of thorns can have a good and bad effect on coral reefs. It has a good effect on them by increasing diversity on the coral reefs by not allowing one species to overgrow. While on the other hand, it can cut down coral population by 90%. Ecologists are trying to find ways to decrease the number of crown of thorns in the ocean. They have tried things such as burying them on shore and injecting them with poison. They are still trying to come up with better ways to deal with them.
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Video Website:
http://www.oceanfootage.com/stockfootage/Crown_Thorn_Sea_Star
Works Cited:
"Asterozoa: Fossil Groups: SciComms 05-06: Earth Sciences." Palaeobiology and Biodiversity Research Group, Department of Earth Sciences, University of Bristol. Web. 15 Oct. 2010.
"The Crown of Thorns." Community Environmental Research in the Pacific Islands. Web. 15 Oct. 2010.
"Crown of Thorns." ReefED - Educate to Keep It Great. Web. 15 Oct. 2010.
"Crown-of-thorn Sea Star." Encyclopedia of Earth. Web. 14 Oct. 2010.
"Crown-of-thorns Starfish." Wikipedia, the Free Encyclopedia. Web. 14 Oct. 2010.
Pictures:
Figure 1: http://www.bubblevision.com/underwater-pictures/racha-noi/images/crown-of-thorns.jpg
Figure 2 & 3: http://www.bubblevision.com/underwater-pictures/racha-noi/images/crown-of-thorns.jpg
Figure 4: http://siera104.com/bio/echin.html
Figure 5: http://www.solcomhouse.com/images/lg_Crown-of-thorns_starfish.jpg
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