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18. Pelagic Cnidaria and Ctenophora
L. Gershwin & M. J. Kingsford
The jellyfishes are conspicuous, but poorly understood,
members of the Great Barrier Reef (GBR) fauna. Much
attention has been given over the past 50 years to two
forms in particular, the so-called ‘box jellyfishes’ and
‘Irukandjis’, both of which are highly dangerous and
are known to kill humans. However, the dangerous
species comprise only a small fraction of the jellyfishes
that make their home in the GBR region.
Jellyfishes in general are among the most intriguing
of animals, because they tantalise the child in all of us
with their strange shapes, often bright colours, and
sometimes flashing lights, and yet, even the milder
stinging varieties seemingly represent the forbidden
signal: DO NOT TOUCH! (Box 18.1.)
While appearing to be simple creatures consisting of
no more than mucus and stinging cells, jellyfish have
great potential to alter ecosystems through predation
and uptake and excretion of nutrients. The medusa stage
is the most obvious and often the most voracious part of
the life cycle; however, the polyp stage represents the
‘seed bank’ of the species, making most jellyfish species
incredibly difficult, if not impossible, to eradicate.
Several well-studied cases exist of jellyfish species being introduced to exotic environments and
BOX 18.1 DID YOU KNOW. . . .
L Box jellyfish are found primarily close to the coast, but Irukandji jellyfish are found on
reefs and islands as well as along the coast.
L There are well over 100 species of jellyfishes that make their home in the GBR region,
and all but about 10 are regarded as harmless.
L At least 10 species of jellyfish are believed to cause Irukandji syndrome, ranging from
as far north as the United Kingdom and as far south as Victoria.
L All jellyfishes are animals with no bones, no brain, no heart, and no lungs or gills.
L Box jellyfish and Irukandjis have well developed eyes with lenses, retinas, and corneas, just like our eyes, and we know experimentally that they can see, even without
a brain!
18. Pelagic Cnidaria and Ctenophora
L. Gershwin & M. J. Kingsford
The jellyfishes are conspicuous, but poorly understood,
members of the Great Barrier Reef (GBR) fauna. Much
attention has been given over the past 50 years to two
forms in particular, the so-called ‘box jellyfishes’ and
‘Irukandjis’, both of which are highly dangerous and
are known to kill humans. However, the dangerous
species comprise only a small fraction of the jellyfishes
that make their home in the GBR region.
Jellyfishes in general are among the most intriguing
of animals, because they tantalise the child in all of us
with their strange shapes, often bright colours, and
sometimes flashing lights, and yet, even the milder
stinging varieties seemingly represent the forbidden
signal: DO NOT TOUCH! (Box 18.1.)
While appearing to be simple creatures consisting of
no more than mucus and stinging cells, jellyfish have
great potential to alter ecosystems through predation
and uptake and excretion of nutrients. The medusa stage
is the most obvious and often the most voracious part of
the life cycle; however, the polyp stage represents the
‘seed bank’ of the species, making most jellyfish species
incredibly difficult, if not impossible, to eradicate.
Several well-studied cases exist of jellyfish species being introduced to exotic environments and
BOX 18.1 DID YOU KNOW. . . .
L Box jellyfish are found primarily close to the coast, but Irukandji jellyfish are found on
reefs and islands as well as along the coast.
L There are well over 100 species of jellyfishes that make their home in the GBR region,
and all but about 10 are regarded as harmless.
L At least 10 species of jellyfish are believed to cause Irukandji syndrome, ranging from
as far north as the United Kingdom and as far south as Victoria.
L All jellyfishes are animals with no bones, no brain, no heart, and no lungs or gills.
L Box jellyfish and Irukandjis have well developed eyes with lenses, retinas, and corneas, just like our eyes, and we know experimentally that they can see, even without
a brain!