Presentation Outline:   Crown of Thorns Starfish

By:  Russell Smith -  Edited by Ray Rector

I.     Introduction

A. Opening Satetement: The Crown of Thorns starfish has recently become a cancer-

    like agent of destruction to coral reef systems worldwide by consuming coral polyps

    at an alarming rate.  Large groups of these starfish, called  outbreaks”, can consume

    and destroy a reef very quickly.


B. Purpose of Research and Presentation

    1. Introduce audience to the environemental crisis created by this reef pest

    2. Inform audience of the characteristics and behavior of the Crown of Thorns

    3. Inform audience of the negative causes and effects surrounding outbreaks.

    4. Inform audience of what is being done to prevent present and future outbreaks


C. Preview of Subtopics Covered

1. Anatomy/Biology

1.     Habitat &  Locations

2.     Life Cycle

3.     Movement

4.     Feeding

5.     Defense Mechanisms and Enemies

6.     Cause & Effect

7.     History of Research

8.     What can be done

II.  Body of Presentation

A. Anatomy

1. Acanthaster Plansi

1.     Generally 14-18 arms

1.     Arms may shed and re-grow in 6 months

2.     Tube feet

2.     Average 25-35 cm in diameter

1.     Up to 80 cm

3.     Colors

1.     Purplelish blue with red tipped spines

2.     Brown and redish grey with red tipped spines

3.     Greenish brown with yellow tipped spines

B. Habitat

1. Prefer sheltered areas such as lagoons

2. Avoids shallow water because of turbulence

3. Deep water along reef front

C. Locations

1. Tropics

2. Indo-Pacific region

3. Not found on reefs in the Atlantic

D. Reproduction

1.     Females shed eggs into water

a.  Up to 60 million per season

2.     Males spawn

3.     Tend to gather together to spawn

4.     High fertilization rate

5.     Spawning

         a. November to January

    b. When the water is warm

6.     After fertilization the egg develops into larvae

7.     Larvae feeds on phytoplankton

8.     Metamorphosis into juvenile starfish

9.     Feeds on encrusting algae for 6 months

10.  Initial feeding on coral at 1 cm size

11.  Full grown and reproductive in 2 years

E. Movement

1. Does not use their arms directly

  a.  Tiny tube feet under the arms

  b.  Tube feet work using hydraulics

2.  Unable to swim

3.  Browses at .25 m/hr over live coral

4. Travels 580 m in a week

4.     Healthy starfish can move up to 1 km between reefs

F. Defense Mechanisms

1.     Molecular sharp crystal tipped spikes

2.     Spikes contain toxic compound called Saponin related to steroids

3.     Toxic to marine life and humans

4.     Can cause nausea and vomiting

5.     Can curl in a ball

G. Feeding

1.     Night feeders

2.     Predatory

3.     Prefered food

a. Staghorn coral

b. Plate corals

4.     Stinging effect of corals are ineffective

5.     Able to shape around the coral

6.     Eat the coral polyps out of their carbonate cups

7.     Extrudes stomach through mouth over the coral

8.     Releases enzymes

9.     Digests the food

10. Single starfish can eat up to 13 square miles per year

11.  Can survive 6 months without food

H. Enemies

1.     Great Triton

2.     White Spotted Pufferfish

3.     Titan Triggerfish

4.     Yellow-faced Triggerfish

5.     Harlequin Shrimp

6.     Bristle or Fire Worm

7.     Humans

I. Causes

1. Human Factors

a. Overfishing

b. Collection of Triton

2. Chemicals

a. Stress the reef

b. Do not affect the starfish

3. Harm predators of the starfish

J. Effects

1. Outbreaks consume entire reef systems

a.  Primary Outbreaks

i. Change in nutrients, temperature, salinity

b. Secondary Outbreaks

i.  Nearby outbreaks, Adult migration, Larvae Drift

ii.  Larvae may drift up to 400 km to infect new areas

c. Becoming more frequent

2. Destruction of the coral

a. Ecosystem suffers

b. Less Food

3. No reef – Increased waves – shore erosion

K. What Can Be Done

1.     Geographical surveys of outbreak-ridden areas

2.     Tracking of movement

3.     Starfish hunts

4.     Save and replenish the Triton

5.     Make interesting ornaments – sell at ocean gift shops

6.     Put more money and effort into research


III.  Summary and Conclusion

A. Review of Subtopics Covered

           1. Outlined the environmental threat to coral reefs caused by Crown of Thorns.

           2. Described the characteristics and behavior of the starfish pest.

           3. Examined the cause and effect relationship of Crown of Thorn outbreaks.

           4. Offered several approaches to reduce and hopefully elliminate outbreaks.  


B. Concluding Thoughts:

     1. Crown of Thorns Starfish are a great threat to the world’s reef ecosystems.

          2. Over fishing of their enemies disrupts the balance to control spread of starfish.

     3. I think it is important to continue research to see if there is a feasible way to

         control the population spread of the Starfish.





Walker, Pam.  2005.  The Continental Shelf.  p. 80.  New York:  Facts on File.


Walker, Pam.  2005.  The Coral Reef.  P. 77.  New York:  Facts on File.


Orme, David and Bird, Helen.  2001.  The Blue Planet:  Seas of Life Ocean World.  p. 30-31.  BBC Worldwide LTD.


Moran, Peter Dr.  Crown of Thorns Starfish Questions and Answers.  Australian Institute of Marine Science.


The Crown of Thorns Strikes Again.


Out of Control.


Kosarek, Nicole and Fabritius, Stephanie.  Acanthaster Planci (crown-of-thorns starfish).


Crown of Thorns Starfish.


Harriot, Vickie, Goggin, Louise Dr., and Sweatman, Hugh Dr.  2003.  Crown of Thorns Starfish on the Great Barrier Reef.  CRC Reef Research LTD