Although it has an innocuous appearance of a flimsy, transparent head and a clusterof long, trailing tentacles, the box jellyfish, Chironex fleckeri or sea wasp is arguably the most poisonous of all animals. . It has claimed the lives of many swimmers in northern Queensland waters and most children have died within minutes of being stung.
    The box jellyfish can be found in coastal waters, creeks and rivers north from 22 degrees south which is the latitude in the vicinity of Mackay, Queensland. Its range is from the north Queensland coast into the Northern Territory and around the northern coastline of Western Australia.
      It  is  most  prevalent  during  the  summer months from November to mid March although stings and deaths have been reported at other times of the year. A hazard to both swimmers and fishermen, the box jellyfish is mostly seen on days when the water is calm. They move into the shallow waters of creeks and rivers in search of prawns which are their main diet. Due to the summer wet season, these waterways are often flooded and muddy making it difficult to see the box jellyfish before its too late.

    The box jellyfish has a body which is sometimes as big as a large bucket. It is box or bell shaped and can weigh more than two kilograms. Up to 16 semi-transparent, extendable tentacles stream out from four projections under the bell. These tentacles in adult specimens can stretch as far as 3 metres and can contract to one quarter of their length.
     Covering the tentacles are millions of stinging capsules which discharge poison through a penetrating thread into the skin of any creature which touches them. A second type of capsule of produces a sticky substance which helps the tentacle stick to the victim.

        The box jellyfish uses its potent venom to catch its prey. Prawns which are its main diet are immobilised and then drawn into the body cavity to be digested.  It travels at a speed around two to three knots and moves by ejecting water from its body cavity; a change in direction can be effected by altering the position of the cavity opening. If suddenly alarmed, it can turn quickly and travel at speeds up to five knots.

       The sting of the box jellyfish is followed immediately  by  excruciating  pain  which increases in mounting waves. Where the skin has made contact with the tentacles, multiple brown or purple lines will appear, making the victim look as if he has been whipped. Death may occur within minutes. The greater the area of contact, the more severe the symptoms.
      The box jellyfish venom contains three different ingredients. The major one causes death by shock to the heart and interferes with the breathing mechanism. Another ingredient attacks the victim's red blood cells. The skin also becomes damaged where the capsules have penetrated. If the victim survives but is not given anti venom, that part of the skin which has been stung becomes ulcerated and is often permanently scarred and discoloured.
      It is highly dangerous to swim at northern beaches during the summer months when this creature is most prevalent. Swimming should be done only at patrolled beaches and only then when local people say it is safe to do so. #