Introduced Species Summary Project
Crown-of-Thorns
(Acanthaster planci)
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Common
Name: Crown-of-Thorns (also CoTs)
Scientific Name: Acanthaster planci
Classification:
Phylum or Division: Echinodermata
Class: Asteroidea
Order: Spinulosida
Family: Acamthasteridae
Genus: Acanthaster
Identification:
Benthic organisms, red echinoderms (starfish) with armored with thorn-like
spines that grow up to 40cm. They live in sheltered areas of reefs and lagoons.
They have 12-18 arms extending from the central body with muscular tubed
"feet" along each arm that function for to move them across the ocean
floor as well as for food gathering and gas exchange. Crown-of-Thorns reach
sexual maturity at the end of their second year, female egg production
increases with size. An adult female CoT can produce 60 million eggs per
spawning. They reproduce sexually once a year in midsummer by releasing eggs
and sperm into the water column that combine to gametes that develop into free-swimming
larvae that swim around for two to three weeks before they then settle on the
ocean floor. A solitary nocturnal feeder, they feed on reef building coral
polyps and take shelter under corals during the day and can live for up to nine
months without feeding. Epithelial cells on the long thorns can release a toxic
chemical (saponins) that is toxic to humans resulting in painful stings that
can last for hours, as well as nausea and vomiting. As with others in the
Echinoderms they are capable of regenerating their arms.
Original Distribution: Indo-Pacific, First identified in 1705 by Georg Rumphius,
and given a scientific name in 1758.
Current Distribution: Acanthaster planci are found on Indo-Pacific coral reefs, the
Site and Date of Introduction: First outbreak was recorded in the 1950s in the
Mode(s) of Introduction: Passive larval distribution traveling in alongshore
currents and adult migration.
Reason(s) Why
it has Become Established: Reduction
of main predators, the Triton Shell, Charonia
tritonis, due to the shell collection trade, larval predation from coral
reef fish has reduced due to overfishing and decimation of coral reefs.
Increased outbreaks have been linked to a number of factors from decreased
predation , increased nutrient run-off, increased salinity, and increased water
temperatures. It is likely that massive outbreaks are as a result of a
combination of factors. Algae blooms from increased nutrients increase larval
vitality and therefore can lead to massive outbreaks.
Ecological
Role: Serves as a prey
for the following species: Giant Triton shells (Charonia tritonis), White-spotted pufferfish (Arothron hispidus), Titan triggerfish (Balistoides viridescens), Yellow-faced Triggerfish
(Pseudobalistes flavimarginatus), Harlequin
shrimp (Hymenocera picta), Bristle
worm (Pherecardia striata). Predation by these species most often occurs
in the larval and juvenile stages, predation of adult CoTs is usually limited
to Triton Shells. Captive CoTs are also vulnerable to infection from a disease
that causes limb disintegration and resulted in massive mortality scientists
are trying to isolate this organism to use in population control.
Benefit(s): Crown-of-Thorns are an important part of reef life and a
driving force of ecological succession, contributing to coral reef diversity,
fossil evidence shows the presence of Crown of thorns, but these outbreaks have
increased in number and scope since the 1970's.
Threat(s): A prolific starfish, the Crown-of-Thorns voraciously feeds
on predator upon scleractinean corals, by extruding
its stomach over the coral community and externally digesting the coral polyps
with their stomach enzymes and absorbing the liquefied coral polyps. They
prefer to feed on branching and tabular reef building corals, Acropora spp. Can decimate a coral community already stressed by increased
nutrient levels and bleaching episodes due to increased temperatures.
Control Level Diagnosis: Capable of massive outbreaks due to free-swimming larva
traveling in the water column, they can decimate a coral community quite
rapidly and can feed on up to 13 square miles of coral per year. Outbreaks have
increased since the 1970's and proliferation has been linked to increased water
temperatures and increased nutrient run-off due to pollution. These outbreaks
have been divided into two forms, primary outbreaks as a result of changing
environmental factors and secondary outbreaks which are as a result of larval
blooms. Coral reefs often cannot fully rebound from massive outbreaks, fast
growing corals can rebound in 15 to 20 years if no other outbreaks occur and
other factors do not contribute to poor reef health. Slow growing corals such
as Porites can take up to 500 years
to recover. Outbreaks generally last up to 5 years on individual reefs but can
last up to 20 on more complex reef systems.
Control Method: Almost 15 million CoTs have been either killed or removed
from the Indo-Pacific area in the past 15 years, the largest program being in
the
Author: Sophie
DeLaCour
Last Edited:
References:
Madl, P. Salzburg,
http://www.sbg.ac.at/ipk/avstudio/pierofun/planci/planci.htm
Kosarek, N. 2000.
"Acanthaster planci" (On-line), Animal Diversity Web. Accessed
Moran, Peter John.
1988 Crown-of-thorns starfish questions and answers. Australian Institute of
Marine Science
www.aims.gov.au/pages/reflib/cot-starfish/pages/cot-000.html
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