Drifting at any depth in all the world’s oceans, these creatures
range from an Arctic species with a bell the size of a car,
to a venomous microscopic Australian. Carnivorous predators,
jellyfish swarm around our coasts and litter our beaches, yet
we know surprisingly little about them. Some of the most
recognisable species don’t even qualify as true jellyfish. One
such, a Portuguese Man of War (Physalia physalis), its
inflated bladder keeping it poised at the surface, is not even
a single animal, but a sizeable colony containing four types of
minute, highly modified polyps.
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Written by MARGO WHITE
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Playing host to larval fish at a depth
of 24 m off subantarctic Campbell
Island, a large Cyanea sp. looks like
an exploded ball gown. This animal
is likely to be a lion’s mane jellyfish
(C. capillata), or—if there are raised
gelatinous warts on the (unseen)
surface of its bell—the recentlydescribed endemic species of Cyanea.
For shrimps and small fish, pelagic
jellyfish of this sort act both as a
floating cafe and a predator fence as
they drift in open seas.
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JELLYFISH
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A male tern heads out at
low tide to find fish in the
shallows. More important than feeding himself
at this time of year is
bringing back food. His
prowess as a provider
makes him irresistible in
the mating stakes.
A female Aurelia sp. (left) broods many
thousands of planula larvae that make
up the white-edging of her oral arms.
Many species of New Zealand jellyfish
were first described in other parts of
the world, a number by German biologist Ernst Haeckel, who illustrated them
vividly, particularly in Kunstformen der
Natur (opposite). While the spectacular
Cyanea genus is found in New Zealand
waters, this species, named for
Haeckel’s late wife Anna Sethe, is not.
Jellyfish keep things simple:
no heart, no brain, no circulatory system and no bones.
They have a pouch for a stomach that doubles as the
reproductive system, a mouth that doubles as an anus,
DURING THE Renaissance, jellyfish
were thought to be plants, and while
18th century naturalists allowed
them entry into the animal kingdom,
they were initially classified as zoophytes, something between plants
and animals.
We don’t generally hold jellyfish
in great regard. If we see them in
the water, we tend to get out. And
while hundreds of people will turn
up to rescue a beached whale, few of
us would stop to re-float a stranded
jellyfish.
And yet humans are probably
responsible for what seems to be an
international jellyfish explosion. In
recent years, there have been reports
from all over the world of uncommonly large blooms of jellyfish
driving people out of the water,
suffocating commercial fish farms
62 | NEW ZEALAND GEOGRAPHIC
and clogging up fishing nets and the
intakes of ships and power plants.
According to numerous scientists,
these blooms suggest that all is not
well within the ocean, perhaps something to do with climate change, pollution, overfishing, or a combination
of all three.
Evidently something is out of balance, but, as many species suffer, the
jellyfish prospers. As larger oceanic
creatures are fished out, there is more
food for jellyfish. They don’t have
many predators, and many of them
are better suited to warmer water.
It seems that one of the most primitive life forms is poised to inherit the
Earth—its watery parts at least.
Some would, and have, argued
that we might as well get used to
eating them, because if we continue
fishing the oceans at the current rate,
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and the rest is mostly water and a bundle of nerves.
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JELLYFISH
A Desmonema like no other hangs like
a question mark in Fiordland. The
highly tannic waters at Isthmus Sound
may offer an explanation for this
animal‘s strange colouring: either
tannins have stained it red or it has
adapted to be more cryptic in this
environment. It is also possible that
the creature’s prey are red and that
it has assimilated their pigment. A
novel diet would hardly be surprising
in Fiordland where a shallow-water
predator, like Desmonema, would find
itself feasting on deep water prey.
The toxic reputation of C. fleckeri,
Australia’s feared box jellyfish, is not
shared by its New Zealand relative,
Carybdea sivickisi (opposite), although
these Cubozoans still inflict a painful
sting. Box jellyfish have complex
structures not found in other
cnidarians. That includes well
developed eyes with lenses, retinas
and corneas, similar to our own, and
displays of sophisticated behaviour
including navigation, light attraction
and courtship—extraordinary given
that they do not have a brain.
there won’t be much else left. “It’s
pretty scary, actually,” says Dr Lisa
Gershwin, curator of natural sciences
at Queen Victoria Museum and Art
Gallery in Tasmania and the former
national marine stinger adviser to
Surf Lifesaving Australia. “There are
many locations around the world that
have flipped to jellyfish-dominated
environments.”
Gershwin is concerned about the
state of the oceans and the fate of
the creatures within it, but she is not
inherently averse to jellyfish. In fact,
she is one of their greatest fans, one of
the world’s few jellyfish experts, and
probably its only jellyfish taxonomist.
“When there’s an international jellyfish conference, it usually means I’ve
gone somewhere,” she says.
Dennis Gordon, editor of The New
Zealand Inventory of Biodiversity and a
principal scientist at NIWA, recently
invited Gershwin to help review
and update the taxonomy of jellyfish
found in New Zealand waters. The
review will be published in the middle of this year, and will include 34
jellyfish, including three new species.
It’s the first time anyone has seriously
looked at local jellyfish for over a century, and it was not an easy task.
Several of the species have been
described in the literature, but many
haven’t been seen since they were first
described. Jellyfish are poorly represented in museum collections, partly
because they are hard to handle and
tend to fall apart, and partly because
nobody has really given them much
attention. Even though this is an island nation where scores of jellyfish
wash up on shores every year, there
isn’t yet a scientist in the country who
has chosen jellyfish as their area of
expertise. Little is known about the
life cycle, ecology or behaviour of our
jellyfish. We’re not even sure if any of
them are endemic.
You have to wonder why none of
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“You can see them in all their diaphanous beauty,
slowly pulsing away…and what could be more
charismatic than a stinging organism?”
the country’s science graduates have
chosen to become a jellyfish expert,
given that the species is of such
medical and public interest. Possibly
because the jellyfish is a brainless,
heartless blob occupying a low bough
on the evolutionary tree of life?
“Well, they do have a simplistic
form,” says Gordon. “But that doesn’t
mean they aren’t interesting. I think
they are incredibly aesthetic. When
you watch them in an aquarium, with
backlighting, and you can see them
in all their diaphanous beauty, slowly
pulsing away, they are quite stunning...and what could be more charismatic than a stinging organism?”
JELLYFISH AREN’T actually fish,
but the word is used to describe a
certain kind of Cnidarian with an
umbrella-like body structure. This
includes Scyphozoans, the true jellyfish; Staurozoans, or stalked jellyfish,
which remain in the polyp stage and
attach to the ocean floor rather than
swim around; Cubozoans, or box
jellyfish; and Hydrozoans, a complex
class of animals that often produce
small medusae resembling simple
jellyfish. The Portuguese Man of
War—which isn’t actually a jellyfish
but a floating colony of individuals—
is a Hydrozoan.
Gershwin and Gordon’s list of
New Zealand species includes six
stalked jellyfish, one box jellyfish and
27 true jellyfish. The most frequently
encountered jellyfish in our parts are
Aurelia, commonly known as moon
jellyfish; Cyanea, commonly known as
lion’s mane; and Desmonema, which
doesn’t have a common name but
could be described as the spotted one.
Lion’s mane and moon jellyfish
can both cause havoc in our commercial fish farms. In 1998, an invasion of moon jellyfish resulted in
the deaths of thousands of salmon
farmed in the waters of Stewart Island. The deaths were probably the
result of jellyfish mucus coating the
gills of the fish and suffocating them,
and their nematocysts irritating the
fish’s skin and causing them to hyperventilate. “They basically slimed
the salmon to death,” says Gershwin.
“They lost 56,000 salmon in 30 minutes. It was horrific.”
The Aurelia is flattish and whitish,
with a fringe of hundreds to thousands of short tentacles around its
margin, plus four tightly held short
oral arms that don’t generally extend
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JELLYFISH
A hydromedusae Aequorea sp. hovers
in Blue Mao Mao Arch at the Poor
Knights, the spray of tentacles around
its bell margin undulating on the
current. Aequorea are able to produce
flashes of bioluminescent blue or green
light—their green fluorescent protein
(GFP) is routinely used as a marker in
molecular biology. Scientists have even
created green glowing mice by inserting the GFP gene.
on top of which they get covered in
slime and stung.”
Small marine arthropods that
do manage to escape the crenulated
drapes of the lion’s mane will undoubtedly get tangled in the sensory
tentacles that trail up to four metres
behind the bell—although the tentacles of the Arctic species of lion’s
mane can be as long as 30 metres.
Tentacles are grouped into eight
clusters, each containing 65–150
tentacles. Each of these in turn is
equipped with thousands, possibly
millions, of nematocysts—stinging darts that fire on contact with
the surface of a prey animal. The
tentacles scoop up the stunned prey
and transfer it to its oral arms, which
pop it into the mouth of the jellyfish,
jellyfish known as ephyra larvae that
grow into the umbrella-shaped jellyfish we all recognise. As they were all
born together and grew up together,
jellyfish tend to stick together, growing from a few millimetres to full size
in a couple of months—sometimes
just to wash up on a beach near you.
MOST NEW ZEALAND beach-goers
know that jellyfish can sting, but generally they get off lightly, compared
with, say, Australians. Northern Australia is unfortunate enough to have
Chironex fleckeri, a type of box jellyfish
regarded as one of the most venomous
creatures on Earth, an animal that
has developed a toxic capacity that far
exceeds its needs. “They do have huge
metabolic demands,” says Gershwin.
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“They do have huge metabolic demands,” says
Gershwin. “But it’s overkill...they could kill a horse.”
beyond the edge of the bell. It has
four distinctive horseshoe-shaped
gonads near the middle of the body.
Desmonema is dome-shaped, whitish, with reddish-brown dots all over
the top of the bell. It has four long,
pleated oral arms, and eight clumps
of long tentacles that extend from the
edge of the bell in a straight line.
The lion’s mane is the largest of all
known jellyfish. Those found in the
Northern Hemisphere can grow up
66 | NEW ZEALAND GEOGRAPHIC
to 2.5 m across, while those found in
lower latitudes, such as New Zealand,
have bells that typically grow to about
50 cm wide. The species grabbed
headlines—“Invasion of the Giant
Blobs”—a couple of years ago when
abnormally large specimens washed
up near Blind Bay on Great Barrier
Island, with the largest measuring 1.5
m across and many others at least 1.2
m across. A large bloom also arrived
in the Coromandel early last year,
many of which were a metre wide.
The lion’s mane has a purple bell
surrounded by what look like layers
of frilly yellow petticoats (its egg
repositories) and metres of long thin
tentacles. One of the new species
described in Gordon and Gershwin’s
review is a type of lion’s mane jellyfish. It is distinct from other lion’s
mane species in numerous structural
features, the most obvious being the
raised gelatinous warts on the exum-
brella (the top of the body), which is
smooth in other species.
The sting of a lion’s mane jellyfish
won’t kill us—some victims have described the sensation as being pricked
by dozens of pins—but small marine
arthropods haven’t got a chance.
“They have these massive curtain-like
oral arms, basically extensions of their
lips, and all these large crenulated
drapes,” says Gershwin. “It’s impenetrable, and tiny things can’t get away...
located somewhere on the underside
of its bell.
Jellyfish move with a form of jet
propulsion—taking water into the
bell and then squirting it out the
back, creating a jet of water that propels the creature forward. They can
also move left to right, but otherwise
go where the ocean currents take
them. Like butterflies and caterpillars, jellyfish have two life stages: the
polyp, like a tiny sea anemone, and
the medusa stage, which is what we
mostly think of as a jellyfish.
Eggs are fertilised internally and
then released as free-swimming larvae—some begin their life hanging
onto their mother’s skirts, or, more
scientifically, their oral arms. They
then develop into polyps, which attach themselves to the sea floor, where
they feed and grow and produce other
polyps, in much the same way as a
bromeliad produces offspring. Some
polyps remain as polyps their entire
life, but others bud off immature
“But it’s overkill because they could
kill a horse.”
Last Christmas an 11-year-old girl
was stung while swimming in the
Calliope River, 23 km inland in Central Queensland. She will be scarred
for life and may need skin grafts—
the venom burned both her legs, a
forearm and part of her stomach. But
given that victims of box jellyfish
typically die within four minutes, she
is fortunate to be alive.
She probably wouldn’t be if it
weren’t for two serendipitous factors. Firstly, her screams attracted
the attention of a couple who doused
her legs with vinegar—which stops
the nematocysts of the box jellyfish
releasing more venom. The man,
whose brother was killed by a box
jellyfish, always carries vinegar with
him. And secondly, her father was
trained in CPR and knew how to
administer first aid before the toxins
locked her heart, after which it would
have been too late.
67
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JELLYFISH
A larval fish tempts fate by swimming
through Desmonema gaudichaudi’s
trailing tentacles—moments later
the fish is sashimi. While not mobile
enough to pursue prey, jellyfish are
effective killers at close range. A
loose network of nerves that link to
a circular nerve ring is ever alert for
stimuli. Contact with the prey triggers
nematocysts— located in specialised
cells called cnidocytes—to pierce the
skin and inject venom.
JELLYFISH
A solitary moon jellyfish (Aurelia sp.)
eclipses the sun in Fiordland (above).
Jellyfish blooms, where thousands
or even tens of thousands of animals
congregate in one location, are not an
uncommon sight. Typically, jellyfish like
Pelagia noctiluca (opposite) swarm in
profusion near the sea surface. These
blooms tend to occur as a seasonal
response to rising temperatures and
upsurges in nutrients and oxygen. A
sudden population spike can also be
the result of increases in salinity, as
iodine is used by polyps to asexually
produce the medusa stage of the
jellyfish lifecycle.
70 | NEW ZEALAND GEOGRAPHIC
Gershwin is very familiar with the
destructive powers of the jellyfish.
She did her PhD on the Irukandji
(Carukia barnesi). This tropical species is only 8 mm in diameter, but
its venom causes a gruesome range
of symptoms, collectively known
as Irukandji syndrome. Along with
unbearable back pain (people describe it as like a drill bearing down
on the spine), increased blood pressure, muscle cramps, vomiting and
diarrhoea, there’s a psychotic effect
in which victims have a sense of impending doom, convinced that they
are going to die. They frequently
beg for the gun. The symptoms usually last about 24 hours, after which
the victim recovers. Between 50 and
100 cases of Irukandji syndrome are
reported in Australia each year. Early
this year, a man from the Philippines
was stung in Queensland while fishing from the deck of a vessel 25 m
above the surface of the ocean. All
it took was a splash of sea spray, and
he ended up in hospital for the next
three days.
Like most of our fauna, New
Zealand jellyfish are more benign.
“You’re lucky,” says Gershwin. “Your
jellyfish are really beautiful, but they
won’t kill you.”
New Zealand does have one box
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A male tern heads out at
low tide to find fish in the
shallows.
Moreare
importVictims
convinced that they are going
ant than feeding himself
to die.
at this
time ofThey
year is frequently beg for the gun.
bringing back food. His
prowess as a provider
makes him irresistible in
the mating stakes.
jellyfish, a diminutive species called
Carybdea sivickisi, which grows to
about a centimeter cube, is transparent with bright orange blobs (the
gonads) and has four orange-striped
tentacles. While its sting isn’t lethal,
it will produce a blister, one that will
hurt and itch before disappearing,
only to return at a later date. “Just
like herpes,” she says. “But it isn’t a virus, it’s an immunological response.”
Fortunately, these seem to be rare in
New Zealand waters; the last was seen
in Cook Strait in 1985.
When Gershwin did her thesis
only one species of Irukandji had
been described, but she has now
identified 14, and 145 other jellyfish
species new to science. Who knows
how many species of jellyfish are in
New Zealand waters just waiting to
be discovered?
“We suspect that there are more
than we know about,” says Dennis
Gordon, who goes on to make a plea
for information from amateur jellyfish enthusiasts. Photographs, notes,
even specimens collected in jars of
ethanol would be extremely helpful
in our understanding of Cnidarian
biodiversity. Divers in particular
should be alert for stalked jellyfish
that live on the ocean floor—there
are at least six species out there, but
nothing is known about their distribution or biology.
According to Lisa Gershwin,
there’s a whole planktonic world just
waiting to be discovered. “Every
time I get the plankton net in the
water I don’t know what’s going to
come up, so I always have this feeling
of Christmas—you’ve got a present,
but you don’t know what’s inside.”
71