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Box jellyfish

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Box jellyfish are water-dwelling invertebrates belonging to the class Cubozoa, named for their cube-shaped medusae. They share many characteristics with their relatives the true jellyfish in the class Scyphozoa. The name sea wasp is also applied to some species of cubozoans, including Chironex fleckeri and Carybdea alata.

Box jellyfish are found in Australia, the Philippines, and many other tropical areas. They are known for the oft-fatal effects of their venom, although not all species are venomous.

Contents

Defense and feeding mechanisms

Box jellyfish use powerful venom contained in epidermic nematocysts to stun or kill its prey prior to ingestion, or as an instrument for defense. Their venom is among the most deadly in the animal kingdom and has caused at least 63 recorded deaths since 1884Williamson J. A., Fenner P. J., Burnett J. W., Rifkin J. (1996). Saving Australia and University of New South Wales Press Ltd, Sydney.. Most often, these fatal envenomations are perpetrated by the largest species of box jellyfish, Chironex fleckeri, owing to its high concentration of nematocysts, though at least two deaths in Australia have been attributed to the thumbnail-sized irukandji jellyfish (Carukia barnesi).Fenner P. J., Hadok J. C. (2004). [Fatal envenomation by jellyfish causing Irukandji syndrome]. Those who fall victim to Carukia barnesi suffer several severe symptoms known as Irukandji syndrome.Little M., Mulcahy R. F. (1998). [A year's experience of Irukandji envenomation in far north Queensland''].

The venom of cubozoans is very distinct from that of scyphozoans, and is used to catch prey (fish and small invertebrates) and for defense from predators. However turtles are unaffected by the sting and eat box jellyfish.

In the Australian summer from November to April or May, box jellyfish are abundant in the warm waters of northern Australia and drive away most swimmers; in order to prevent fresh victims, some popular beaches erect enclosures off shore to keep predators out, though smaller species such as Carukia barnesi can still filter through the net.Nagami, Pamela (2004). Bitten: True Medical Stories of Bites and Stings, St. Martin's Press, 54. ISBN 0312318227. It is not known where they go in the Australian winter. Australian researchers have used ultrasonic tagging to learn that these creatures sleep on the ocean floor between 3pm and dawn. It is believed that they sleep to conserve energy and to avoid predators.

Vision

Some theorize box jellyfish actively hunt their prey—for effective hunting they move extremely quickly (moving at speeds up to 3–3.5 knots (1.5 to 1.8 m/s)) instead of drifting as do true jellyfish, and have an active visual system of 24 eyes located on the center of each side of its bell.

The eyes occur in clusters on the four sides of the cube-like body. Sixteen are simply pits of light-sensitive pigment (eight slit-shaped eyes and eight lens-less pit eyes), but one pair in each cluster is surprisingly complex, with a sophisticated lens, retina, iris and cornea, all in an eye only 0.1 millimeters across

The lenses on these eyes have been analyzed and could form distortion free images. Despite the perfection of the lenses, the retinas of the eyes lie closer to the lens than the optimum focal distance resulting in a blurred image. One of these eyes in each set has an iris that contracts in bright light. Four of the eyes can only make out simple light levels.

It is not currently known how this visual information is processed by Cubozoa, as they lack a central nervous system, although they seem to have four primitive brain-like organs.

Treatment of stings

Pantyhose were once worn by Australian lifeguards to prevent stings. These have now been replaced by lycra stinger suits.

If swimming at a beach where box jellyfish are known to be present, a bottle of vinegar is an extremely useful addition to the first aid kit. Acetic acid, found in vinegar, disables the box jellyfish's stinging cells that have not yet shot into the bloodstream (though it will not alleviate the pain).

If stung, bathe the affected area with liberal amounts of vinegar, remove any attached tentacles and immediately seek medical attention. Removing the tentacles without first applying vinegar may cause more damage and increase the chance of necrosis of the skin. However if no vinegar is available, removal of the tenticles without it is recommended. Vinegar has helped save dozens of lives on Australian beaches. Methylated spirit and alcohol should not be used.

To save the life of the victim, antivenom must be given as soon as possible; this is usually available from hospitals, doctors and clinics, close to where the jellyfish are found. If antivenom is not immediately available, CPR may be necessary to keep the victim aliveThinkquest [link].

It should be noted that, although commonly recommended in folklore and even some papers on sting treatmentZoltan, Todd B.; Taylor, Kenneth S.; and Achar, Suraj A. (2005). [Health Issues for Surfers]., there is no scientific evidence that urine, ammonia, meat tenderizer, sodium bicarbonate, boric acid, lemon juice, or papaya will disable further stingingFenner, P (2000). Marine envenomation: An update — A presentation on the current status of marine envenomation first aid and medical treatments. Emergency Medicine Australasia, Volume 12, Number 4, December 2000: 295-302(8), and indeed these substances may even hasten the release of venom.Ruch, John. [Stupid Question: June 7, 2004]. Retrieved January 29, 2006.

Classification

There are two families of Cubozoa, Chirodropidae and Carybdeidae containing 20 species between them. A phylogenic analysis of their relationships is yet to be published.

References

External links

 

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