One very interesting organism that is found in coral reefs is the crown of thorns star fish. This organism is a large nocturnal starfish that eats and thrives off of coral polyps. They can be up to half a meter in diameter. It received its name from the venomous thorn like spines that cover its entire body. The thorns are very sharp and are capable of penetrating human skin. The thorns release venom when penetrating someone. Although they are not life threatening, it can cause nausea, vomiting, and infection around the wound. It is a threat to tropical coral reefs because they consume corals and leave nothing behind but the coral skeleton. It is a solitary animal which feeds alone. It always maintains distance between itself and other members of its species. However, when it feeds the thorns release a powerful chemical which attract other star fish to the area.
The crown of thorns starfish is a carnivorous predator because consumes coral polyps. It does this by attaching itself to corals and extruding its stomach onto the coral. It basically turns its stomach inside out while feeding and sucks its stomach back in when it’s done feeding. By doing this it releases digestive enzymes on to the coral. It does this in order liquefy the coral tissue and absorb its nutrients. A single starfish can consume about 6 square meters of coral per year. It can live for up to 6 months without eating anything by using its energy reserves.
COT starfish typically like to live near coral reef passes. By doing this they help keep the passes open. They like to live in places where there is little disturbance from tides, currents, or weather. COT starfish are nearly invisible to the human eye until they are about 6 months old. They remain in the rocks and rubble until this time. A single female starfish is capable of releasing millions of eggs during its breeding season (Nov to Jan). They do this when the water is at the right temperature which is about 28 degrees Celsius. There is little connection between lunar or tidal patterns and spawning.
Within recent years due to over fishing the number of predators that go after COT starfish has greatly diminished. This overpopulation of COT starfish causes great destruction of the coral reefs. This causes the other colorful reef organisms to migrate to living corals. Outbreaks of this organism usually occur in places with a high level of nutrients available. The nutrients often accumulate in areas of high terrestrial runoff. When moving to different areas there movement can be disrupted by soft sandy areas which are difficult for them to travel on. They can move up to 20 meters in an hour. After leaving an area the area often becomes filled with high levels of algae causing most living organism to move somewhere else. Coral reefs can still support the COT starfish without being destroyed as long as their numbers stay relatively low. It can support up to 30 of them over 10,000 square meters. Out breaks are not always negative because it is argued that they increase biodiversity in coral reefs which is essential for coral reefs to thrive.
References:
"The Crown of Thorns." Community Environmental Research in the Pacific Islands. Web. 05 May 2011.
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"Crown-of-thorn Sea Star." Encyclopedia of Earth. Web. 05 May 2011. .
Sheppard, Charles, Simon K. Davy, and Graham M. Pilling. The Biology of Coral Reefs. Oxford: Oxford UP, 2009. Print.
Sverdrup, Keith A., and E. Virginia Armbrust. An Introduction to the World's Oceans. Dubuque, IA: McGraw-Hill, 2009. Print
