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Crown of Thorns Starfish

Page history last edited by PBworks 17 years, 9 months ago
Crown of Thorns Starfish

 


Description and Rationale

 

The Crown-of-Thorns starfish is one of the largest starfish to be recorded, and it plagues the coral reefs in the tropics from the Red Sea, through the Pacific Oceans, and over to the Pacific coast of Panama.  These starfish can live without seriously threatening the coral reefs, but then when an outbreak occurs, the corals are put in serious danger.  After an outbreak occurs, there is a great number of COTS (Crown-of-Thorns starfish), and they begin eating in aggregations.  This causes great damage to the coral reef.

What is the COTS impact on the daily lives of those depending on the ocean for survival?  Is it a predator of the main resources of the Filipinos?  Are many people harmed by the starfish’s sharp venomous thorns? What other parts of the ocean are the COTS harming? Can removing the COTS do any harm to the coral reef?  Is the danger of removing the COTS worth the danger of keeping them in the coral reefs?

Currently the Crown-of-Thorns starfish is simply viewed as a harmful starfish not having any benefits to the ocean at all.  There are many organizations trying to figure out a way to kill COTS completely.  However, they fear in the process they will throw off the coral reef ecosystem.  Possibly there is an unknown benefit of these starfish that would be revealed after the total loss of them all.  It is risky to get rid of them when it is possible they are performing a task helping the ocean in some way.  It is a possibility that they are trimming the coral reefs to help keep the passes open. 

The initial purpose of this project will be to research the biology and ecology of the Crown-of-Thorns starfish, focusing mainly on those living in the coral reefs of the Philippines.  This will be done through research as well as interviews with people who have experience with COTS and/or those who have knowledge of those who rely on the ocean for survival or for business.  These findings will help further the knowledge of whether or not COTS can be beneficial to the coral reefs, or if they are simply a harmful creature in need of killing. 

It is hoped that unknown uses of the highly disliked and avoided Crown-of-Thorns starfish will be discovered and will be able to contribute to the betterment of the Filipino people.     

 

 

 

 

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Biology

 

Common Names and Synonyms

 

The Acanthaster planci is more commonly known as the crown-of-thorns starfish.  For short, scientists often refer to the crown-of-thorns as COTS.  By taking one look at this starfish, one would be able to assume the reason it was given the name it was.  It is covered with thousands of sharp needles, or thorns.    

 

Classification

 

Kingdom: Animalia 

Phylum: Echinodermata

Class:  Asteroidea (starfish)

Order:  Spinulosida

Family: Acanthasteridae

Genus:  Acanthaster

Species: Acanthaster planci

 

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Morphology and Physical Description

The crown-of-thorns starfish vary in color depending on their diet and their habitat.  They use their thousands of thorn-like spines for protection.  These spines cover the starfish on all surfaces of its body.  The spines on the top of the starfish are 4-5 centimeters in length.  The tips of the spines have a molecularly sharp crystal point.  These are so sharp they slide right into skin, leaving their venom, a nerve toxin.

The spines underneath the starfish are flat and soft, fitting along the grooves of the bottom of the starfish.  The spines on the side of the starfish make a barrier of crossing spines, so the starfish is well prepared for defense.

The joints of the starfish move as a result of the connection between the primary aboral (away from the mouth) spine and its pedicel (an ultimate division of a common peduncle).  This connective tissue in the joints was studied and discovered to be made mostly of collagen fibers.  The muscle fibers of the starfish are mainly found in this connective tissue, at the central holes.

 

 

 

 

Getting Food

 

Crown-of-thorns starfish feed on coral polyps, digesting them very uniquely.  The starfish expels its stomach over the coral colony, emitting digestive enzymes which then absorb the liquefied tissue.  While eating, the starfish maintain a distance from each other, feeding mostly at night time.  These starfish can survive for six months at a time during food shortages because they have stored energy.  Each individual starfish can eat up to thirteen square miles of coral per year, and in recent years have greatly decreased the colorful diversity of the Great Coral Reef.

 

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Reproduction

 

Acanthaster planci reproduce sexually.  As of current knowledge of their reproduction, the starfish are unable to reproduce asexually.  Their spawning season is around November to January, when the water temperature is at its warmest.  The female starfish release their eggs into the water, and then is fertilized by the surrounding males’ sperm, which they also release.  Roughly sixty million eggs can be produced by a large female starfish (about 40 centimeters in diameter) in just one spawning season. 

 

Environmental Factors

 

 The starfish live and feed primarily on the coral reefs.  When under controllable numbers, the starfish does not pose a huge threat to the reefs.  However, when the starfish number grows to the point that it consumes the coral quicker than the coral grows, it causes serious dangers.  This occurrence is referred to as an ‘outbreak’.  Outbreaks have been a major concern on the Great Barrier Reef for over 40 years.

One predator of the starfish is the triton.  The triton are being captured and sold as souvenirs because of their very attractive shell.  Some believe that this is a cause for the increase in the crown-of-thorns population.

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Origin and Distribution

 

The Acanthaster planci was first discovered in 1705 in the Indo-Pacific by a man named Georg Rumphius, and given its name in 1758.  The first outbreak of the starfish was in the 1950’s in the Ryukyu Islands.  Also, other early outbreaks occurred on Green Island and on the Great Barrier Reef in the 1960’s.  The starfish are now commonly found on Indo-Pacific coral reefs, the Red Sea, Australia’s Great Barrier Reef, Hawaii, Palau, Guam, Japan, Micronesia, American Samoa, the Cook Islands, Fiji, the Maldives, and East Malaysia.

 

Importance to People

 

One benefit of the crown-of-thorns starfish is the biodiversity it gives to the coral reefs.  When in reasonable numbers, they do not do serious damage to the coral reefs.  The starfish have inspired scientists to do more research about sea life and the coral reefs and as a result, scientists have gained a great deal of new knowledge.  Specifically, scientists have acquired information involving thyroxin-accelerated larval development, as well as temperature effects on larval development.

Crown-of-thorns starfish are usually viewed as a negative influence to the sea.  They are said to terrorize the coral reefs and putting the whole ecosystem in danger.  This could be consequential to those who rely on the coral reefs for a way of life, such as those relying on the coral reef ecosystem for fish and other protein.  As well, for those working or living in areas infected with the starfish, a threat is posed because of the poisonous spines on the animal itself.  When humans are accidentally poked with a spine, the toxin is injected into their body, causing damage to their nerves.  The damage is sometimes permanent, and sometimes only temporary.  One woman was pricked on the finger by a spine of the starfish, and had an irregular growth of her fingernail for several months after.

 

Survivability and Endangered Status

 

The crown-of-thorns starfish are actually increasing in number, as a result of the decrease of the tritons.  The tritons feed on the larva of the starfish, and as the tritons decrease, the larvas are being able to fully develop into an adult starfish.  In many places, the collection of tritons has been banned.  However, tritons are still being sold in gift shops, and nobody has been fined for doing so.  The laws are placed, but not enforced.  Since the 1970’s, crown-of-thorns have greatly increased, which is viewed by some as an environmental disaster.  Resolutions to this problem are currently being researched by many.     

 

 

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Potential Solutions

 

Are there any potential beneficial uses of the Crown-of-Thorns starfish?  It has not been established at this point by this researcher if the starfish will continue to be a harmful part of nature that people will be forced to continue to deal with, or if it will result in being a useful part of livelihood of the people living around them.  Further research about the possible uses of the starfish’s body will have to be done as well as field studies.  There are many ideas but none of which have been confirmed.  Below are two possibilities with an analysis of the advantages and disadvantages of each.  Along with each possibility is a current update of the progress made on each possibility. 

 

Possibility 1  TOURIST CURIO

 

In interviews of those in the Mexican echinoderm trading industry, it was discovered that there is an estimated 62 sea star fishers.  These fishers collect roughly 12,000 starfish each year.  Also, at least 200 retail stores in major tourist trading centers in Mexico sell star fish as souvenirs.  In Cebu, there are many people who dry starfish and sell them as tourist curio.

 

Advantages:

 

1. The overpopulated island of Olango is located only 5 km east of Mactan Island, a major tourist attraction in Cebu.  Currently, the residents of Olango find the  presence of tourists annoying and a disturbance to their way of life.  The tourists scuba dive and fish freely in the waters where the people are trying to make their  living.  The people of Olango could easily take advantage of the overwhelming  existence of constant tourism on their island.  Taking the Crown-of-Thorns starfish from the water, drying them, and selling them to the tourists could  provide a steady income for many families.  This industry could perhaps be more reliable than that of the fishing industry, as the tourists will always be there, and the presence and quality of fish can waver.

2. The mass amount of collection of the Giant Triton for tourist curio has caused an increase in the numbers of the Crown-of-Thorn starfish.  The triton is the main predator of the starfish.  With the tourist curio focused more on the starfish,  possibly the focus can be taken off of the popularity of the triton shell.  Not only  would there be a decrease of the starfish because they are being collected for the curio, but also because there would be an increase in triton again.   

 

Disadvantages:

 

1. Most starfish used for curio are different species of starfish than that of the Crown-of-Thorns.  They are generally spine-less and are not poisonous.  These are two characteristics of the Crown-of-Thorns that would have to be dealt with carefully.  While collecting the starfish, the people would have to be very aware  of the present danger. If poked with a spine of the starfish, a nerve toxin will be released into their bodies and could cause permanent damage to the person.  One story reports that a woman was pricked with a spine on her finger and for months after had irregular nail growth on that finger. 

2. The Crown-of-Thorns has generally been viewed as an ugly creature.  Because of  this, it’s not certain that they would be a huge hit among tourists.  However, as they say, beauty is in the eyes of the beholder.  

 

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Possibility 2  INFORM PEOPLE

 

Action Step

 

In many places such as the Philippines, the people making their living off fishing in the waters plagued with the Crown-of-Thorns are poor and probably have not had a complete education, if any at all.  If there is something they can do about the starfish, or some way they can use them to benefit their livelihood, someone has to tell them.

 

Advantages:

 

1. Uneducated people trying to make a living could become more familiar and aware  with what is going on inside the water in which they fish.  Being more familiar with it could help them improve their methods of fishing.  As well, being more  aware of the presence of the Crown-of-Thorns could prevent any injury caused by  them.  The starfish sometimes dwell in shallow waters, which could mean very possible and very dangerous injury for these people, who work in the water everyday.

2. Many popular scuba diving sites are the homes to the Crown-of-Thorns starfish.  Informing the scuba divers of the starfish is greatly important so that they will not hurt themselves by being poked by a spine of the starfish.  If the divers do not know what the starfish is, they might not be as alert not to touch it.   

3. The Bible commands us to give to those in need.  Giving people a way to be better informed about their environment to help them better their livelihood obeys this command.  By informing them, we can help them learn and improve, instead of just ignoring their problems, and withholding the information that we have which could greatly benefit them.

 

Disadvantages:

 

1. It is not a guarantee that people knowing about the Crown-of-Thorns starfish will change the effect they are having on the environment.  It is also not a guarantee that my brochure will reach the people who are most effected by the starfish.  It is difficult to find those involved with this matter, and to get the knowledge to them.  It can only be hoped that my brochures will be effective. 

 

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Bibliography

 

 

 

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