To most swimmers, jellyfish are horrible things to be avoided, but to divers, protected from stings in our wetsuits, jellyfish are a thing of beauty as the glide through the water.
There are more than 1800 different species of salt water jellyfish and several fresh water specimens. They are free swimming from the phylum Cnidaria. They don’t have any kind of respiratory system – this is why their skin is so thin – they can absorb oxygen through it from the water. They also don’t have a conventional digestive system, simply absorbing nutrients directly through their digestive cavities.
Some varieties spend most of their time actively swimming, by “pulsing” their bodies, while others simply flow with the current. They don’t have vision as such, but most species have some light sensitive organs which can help to orientate themselves to the surface.
Their appearance is often seasonal, and varies according to sea temperature. In good conditions, up to 100,000 can be seen in one area – this phenomenon is known as a “bloom.” They don’t have natural predators, so in certain conditions, their numbers can increase dramatically. Their lifespan varies from a few hours to several months.
Jellyfish are considered a delicacy in the far east, and after careful preparation, can be served raw or cooked. The preparation involves salting and drying for a number of days, before serving shredded with a dip of soy sauce.
All jellyfish stings are painful, and some (such as a box jellyfish sting) can be fatal. The tentacles have stinging cells in them, which literally fire venom into the victims body. The stings are acidic, so a strong alkalis will provide relief – vinegar, urine and baking soda will all help. If in doubt, get someone to pee on you! Any remaining jelly on the skin should be removed carefully using gloves.
Box jellyfish, or Cubozoa, are among the most venemous creatures on the earth. Each tentacle has up to 500,000 stingers which will inject venom into the victim, and a sting often results in death.
So that’s the story of the jellyfish – beautiful, but potentially painful or even fatal.
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