Chironex fleckeri, commonly known as the sea wasp, is a
species of deadly venomous box jellyfish found in coastal waters from northern
Australia and New Guinea north to the Philippines and Vietnam. It has been
described as "the most lethal jellyfish in the world", with at least
63 known deaths in Australia from 1884 to 1996.
Notorious for its sting, C. fleckeri has tentacles up to 3 m
(10 ft) long covered with millions of cnidocytes which, on contact, release
microscopic darts delivering an extremely powerful venom. Being stung commonly
results in excruciating pain, and if the sting area is significant, an
untreated victim may die in two to five minutes. The amount of venom in one
animal is said to be enough to kill 60 adult humans, although most stings are
mild and do not require hospitalization.
When the jellyfish are swimming, the tentacles contract so
they are about 15 cm long and about 5 mm in diameter; when they are hunting,
the tentacles are thinner and extend to about 3 m long. The tentacles are
covered with a high concentration of stinging cells called cnidocytes, which
are activated by pressure and a chemical trigger; they react to proteinous
chemicals. Box jellyfish are day hunters; at night they are seen resting on the
ocean floor.
In common with other box jellyfish, C. fleckeri has four
eye-clusters with 24 eyes. Some of these eyes seem capable of forming images,
but whether they exhibit any object recognition or object tracking is debated;
it is also unknown how they process information from their sense of touch and
eye-like light-detecting structures due to their lack of a central nervous
system. During a series of tests by marine biologists including Australian
jellyfish expert Jamie Seymour, a single jellyfish was put in a tank. Then, two
white poles were lowered into the tank. The creature appeared unable to see
them and swam straight into them, thus knocking them over. Then, similar black
poles were placed into the tank. This time, the jellyfish seemed aware of them,
and swam around them in a figure-eight. Finally, to see if the specimen could
see colour, a single red pole was stood in the tank. When the jellyfish
apparently became aware of the object in its tank, it was seemingly repelled by
it and remained at the far edge of the tank.[citation needed] Following these
experiments, the Australian researchers put forward the idea of red safety nets
for beaches (these nets are usually used to keep the jellyfish away, but many
still get through its mesh). The test was repeated, with similar results, on
Irukandji jellyfish, another toxic species of box jelly.
Chironex fleckeri lives on a diet of prawns and small fish,
and are prey to turtles, whose thick skin is impenetrable to the cnidocytes of
the jellyfish.
