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Bluebottles and Pacific man-o-war
Physalia species cause stings that are similar to those
from jellyfish although these animals are siphonophores (hydrozoans)
and not jellyfish (scyphozoans and cubozoans). About 10-30,000 stings
each year are reported along the east coast of Australia from Physalia
with about 500 reported from Western Australia and South Australia.
No fatalities have been confirmed from these animals in the Southern
Hemisphere but there have been several fatalities from related species
in the Northern Hemisphere.
Photo by Lisa-ann Gershwin
Instead of the usual jellyfish bell, Physalia have a gas-filled
sac that floats on the surface of the water and tentacles that hang
underneath. Physalia can change the orientation of its
float and use it to ‘sail’ with the wind. There are
stinging cells (or nematocysts) in rows along the tentacles. The
life cycle of these stingers is not known.
The bluebottle Physalia utriculus is Australia’s
most common species. It has a blue float usually 20-80mm long (but
can be up to 150mm long) which is wrinkled on the top. The bluebottle
has a single main retractile tentacle hanging from the float that
can be contracted to a few centimetres or extended to several metres
long. Many shorter smaller tentacles may also hang from the float.
The bluebottle is found in vast numbers on the eastern Australian
coast every year. They also occur in South and Western Australia.
The sting causes immediate pain which can last more than an hour.
The pain is usually in the lymph glands draining the arms and legs.
It is possible that there are two other species of Physalia
that are much larger than the bluebottle and have both been called
Pacific man-o-war. The Pacific man-o-war is related to the Portuguese
man-o-war from the Atlantic Ocean. The float of the Pacific man-o-war
is 100-150mm long compared with the Portuguese man-o-war which has
a float which can be 250-300mm long. The float of the Pacific man-o-war
has 7-8 long retractile tentacles and many shorter, fine tentacles
hanging from it. The long retractile tentacles can be extended to
10 metres long. The Pacific man-o-war causes a sting which is more
painful than those from the bluebottle. The pain can be relieved
by cold packs. In some cases, the victim may suffer a moderate Irukandji-like
syndrome with back pain, and muscle cramps in the limbs, abdomen