CROWN OF
THORNS STARFISH
(Acanthaster plancii)
The crown of thorns starfish is an
amazing inhabitant of the coral
reef. The largest of the coral
reef starfish, it is covered with
large, poisonous spines. Its
colour is highly varied, ranging
from bright orange to ruddy reds
or bluey purples. Though able to
inflict an extremely painful
wound, its main notoriety is that
it eats coral. It does this by
extruding its stomach out of its
body and on to the coral surface.
It then works its way over the
coral, digesting the tissue as it
goes. In high numbers, vast areas
can be denuded by their collective
appetite. |
|
Since the early
description of the occurrence of large
numbers from the Great Barrier Reef and
Guam in the early to mid 1960s, this
coral-eating starfish has been subjected
to intense study. Normally quite rare,
its numbers are seen to increase to
plague proportions throughout the Indian
and Pacific Oceans and the Red Sea, and
seemingly with increasing frequency.
In Fiji, the outbreaks have been
documented many times. Elders in some of
the villages recall early outbreaks but
feel that they are occurring more often.
Is this related to the El Nino? Some
scientists think so. Whatever the
trigger, large areas are eaten when
these immense numbers are on the move.
Is this a disaster? If you are relying
on a coral reef for a dive location,
then the answer is yes. Otherwise, the
infestation can be likened to a
bushfire, such as with coral bleaching,
where rapidly growing corals are removed
with the subsequent recolonisation by
the less competitive corals. The
parallel with coral bleaching continues
with the implication of outbreak
frequency with the El Nino events, or
the questions which remain unanswered as
to the role of the infestations in the
longer term cycles of the coral reef.
|