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Crown of Thorns Starfish

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Introduction

Crown of Thorns Starfish - Out of Control Johanna Davey The Crown of Thorns starfish (Acanthaster planci) lives on tropical coral reef systems ranging from the Red Sea, throughout the Indian and Pacific Oceans, and all the way to the Pacific coast of Panama. The can grow to 40cm in diameter however some have been known to reach almost half a metre. The starfish have 16 to 18 arms covered all over with long, venomous spines. They range in colour from purplish-blue with red tipped spines to green with yellow-tipped spines. Their colour may vary somewhat depending on the individual starfish's diet. Crown of Thorns starfish feed predominantly on staghorn and plate corals (genus Acropora). They appear to avoid massive corals and branching colonies of coral as these often contain small crabs and shrimp that defend their coral habitat from predators such as the Starfish. This preference of specific coral species over others has often resulted in the sparing of some clusters of coral amongst the destruction of an entire reef habitation. Coral is naturally avoided by the majority of marine life as coral all have nematocyst containing stinging cells. Crown of Thorns starfish are not affected by this defence mechanism. This peculiar diet has caused them to evolve into extraoral feeders. An extraoral feeder is capable of forcing its stomach through its mouth. ...read more.

Middle

Tritons are slow growing and the bigger they are the more eggs they lay yet the bigger the shell is the easier it is to be spotted by divers looking for an easy dollar. This market is thought by some as the reason for the increase in starfish numbers. The Humphead Maori wrasse is an active CofT predators and is able to consume more than the Giant Triton. The Humphead Maori Wrasse has historically been taken in the Great Barrier Reef line fishery - and more recently in the live fish fishery - From December 2003, it became illegal to fish for the Wrasse under Queensland fisheries laws. The swell in human activity along coastlines has caused an increase in fertiliser runoff. This fertiliser does exactly what it was designed to do, helps plants to grow. Algae growth has caused damage to coral and thus the damage is increased along with that already caused by the starfish. In some countries fishing methods are not regulated. Dynamite is often used to stun fish so that they can be easily plucked from the surface. This has devastating effects on the reef systems. It is often thought that Crown of Thorns starfish are able to sense damaged coral and aggregate in that area as they know an easy meal can be obtained. This has not yet been proven yet if true it could vastly increase the damage already sustained by the area. ...read more.

Conclusion

the ocean * No side effects or damage to other species * * Labour intensive * Practically useless as CofT can move quickly from one area to another * Needs to be done almost daily just to protect a small area * Expensive Introducing a Virus/Disease Advantages Disadvantages * Once disease or virus in order can spread easily and quickly * Could affect other species * Cannot be recalled * Expensive to research * Needs to be carefully monitored for damage to other species or the environment * CofT are a natural part of the reef and a time would be needed to stop the spread of the disease to allow some CofT to remain The Crown of Thorns starfish are a natural part of the reef ecosystem however over the past 50 years numbers have boomed. This is thought to be due to a decrease in predators for all starfish ages and an increase in planktonic food available to larval starfish. The increase of starfish could not only affect habitats of many species of fish but it could also cause extensive loss to the tourism economy that depends heavily on the reef. The current methods of eradicating the starfish (Physical Removal) are expensive and barely effective. The starfish move back just as fast as they are removed. They are short term solutions and unless a more successful control method is put in place reef systems around the world could be damaged permanently. ...read more.

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