Jellyfish

Jellyfish are marine invertebrates belonging to the class Scyphozoa of the phylum Cnidaria. They can be found in every ocean in the world and in some fresh waters. The term "jellyfish" is a common name, and therefore does not imply any systematic relationship to vertebrate fish -- jellyfish are cnidarians. The term "jellyfish" is also applied to some close relatives of true scyphozoans, such as the Hydrozoa and the Cubozoa.

Jellyfish
Sea nettle, Chrysaora quinquecirrha
Scientific classification
Kingdom:	Animalia
Phylum:	Cnidaria
Class:	Scyphozoa Goette, 1887
Orders
Stauromedusae Coronatae Semaeostomeae Rhizostomae

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Since jellyfish are not fish, some people consider the term "jellyfish" a misnomer, and instead use the term "jellies" or "sea jellies". The word "jellyfish" is also often used to denote either hydrozoans or the box jellyfish, the cubozoans. The class name, Scyphozoa, comes from the Greek word skyphos, denoting a kind of drinking cup and alluding to the cup shape of the organism.

A group of jellyfish is often called a "smack". ^[1]

Culinary uses

Jellyfish are an important source of food to the Chinese community and in many Asian countries.^[2] Only jellyfish belonging to the order Rhizostomeae are harvested for food. Rhizostomes (especially Rhopilema esculentum, Chinese name: 海蜇 hǎizhē) are favoured because they are typically larger and have more rigid bodies than other scyphozoans. Traditional processing methods involve a multi-phase procedure using a mixture of table salt and alum, and then desalting.^[2] Processing makes the jellyfish drier and more acidic, producing a "crunchy and crispy texture."^[2] Nutritionally, jellyfish prepared this way are roughly 95% water and 4-5% protein, making it a relatively low calorie food.^[2]

In biotechnology

In 1961, green fluorescent protein was discovered in the jellyfish Aequorea victoria by scientists studying bioluminescence. This protein has since become a quite useful tool in biology. Its use is mainly for scientists studying in which tissues genes are expressed. The technique uses genetic engineering fuse the gene of interest to the gene of GFP. the fused DNA is then put into a cell, to generate either a cell line or (via IVF techniques) an entire animal bearing the gene. In the cell or animal, the artificial gene gets turned on the same tissues and the same time as the normal gene. But instead of making the normal protein, the gene makes GFP. You can then find out what tissues express that protein, or at what stage of development - by shining light on the animal or cell, and looking for the green fluorescence. The fluorescence shows you where the gene you are interested in is expressed. ^[3] Jellyfish are also harvested for their collagen, which can be used for a variety of scientific applications including the treatment of rheumatoid arthritis.

In captivity

Jellyfish are commonly displayed in aquaria in many countries; among them the Monterey Bay Aquarium, Long Beach Aquarium of the Pacific, Vancouver Aquarium, New York Aquarium,Seattle Aquarium, New England Aquarium, Newport Aquarium, National Aquarium in Baltimore, Georgia Aquarium and Maui Ocean Center. Often the tank's background is blue and the animals are illuminated by side light to produce a high contrast effect. In natural conditions, many jellies are so transparent that they are almost impossible to see.

Holding jellyfish in captivity presents other problems. For one, they are not adapted to closed spaces. They depend on currents to transport them from place to place. To compensate for this, professional exhibits feature precise water flows, typically in circular tanks to prevent specimens from becoming trapped in corners. The Monterey Bay Aquarium uses a modified version of the kreisel (German for "spinning top") for this purpose.

Toxicity to humans

When stung by a jellyfish, first aid may be in order. Though most stings are not deadly, some stings, such as those of the box jellyfish (Chironex fleckeri), may be fatal. However, even nonfatal jellyfish stings are known to be extremely painful. Serious stings may cause anaphylaxis and may result in death. Hence, people stung by jellyfish must get out of the water to avoid drowning. In serious cases, advanced professional care must be sought. This care may include administration of an antivenin and other supportive care such as required to treat the symptoms of anaphylactic shock. The most serious threat that humans face from jellyfish is the sting of the Irukandji, which has the most potent and deadly venom of any known species.

There are three goals of first aid for uncomplicated jellyfish stings: prevent injury to rescuers, inactivate the nematocysts, and remove any tentacles stuck on the patient. To prevent injury to rescuers, barrier clothing should be worn. This protection may include anything from panty hose to wet suits to full-body sting-proof suits. Inactivating the nematocysts, or stinging cells, prevents further injection of venom into the patient.

Vinegar (3 to 10% aqueous acetic acid) should be applied for box jellyfish stings.^[4][5] Vinegar, however, is not recommended for Portuguese Man o' War stings.^[4] In the case of stings on or around the eyes, vinegar may be placed on a towel and dabbed around the eyes, but not in them. Salt water may also be used in case vinegar is not readily available.^[4][6] Fresh water should not be used if the sting occurred in salt water, as a change in pH can cause the release of additional venom. Rubbing the wound, or using alcohol, spirits, ammonia, or urine will encourage the release of venom and should be avoided.^[7] Though often not available a shower or bath as hot as can be tolerated can neutralize stings. Be careful with this method if hypothermia is also suspected.

Once deactivated, the stinging cells must be removed. This can be accomplished by picking off tentacles left on the body.^[7] First aid providers should be careful to use gloves or another readily available barrier device to prevent personal injury, and to follow standard universal precautions. After large pieces of the jellyfish are removed, shaving cream may be applied to the area and a knife edge, safety razor, or credit card may be used to take away any remaining nematocysts.^[8]

Beyond initial first aid, antihistamines such as diphenhydramine (Benadryl) may be used to control skin irritation (pruritus).^[8] To remove the venom in the skin, apply a paste of baking soda and water and apply a cloth covering on the sting. If possible, reapply paste every 15-20 minutes. Ice can be applied to stop the spread of venom until either of these is available.

• Australian spotted jellyfish (Phyllorhiza punctata).

• Catostylus species of stingless jellyfish from Palau, Micronesia.

• West Coast Sea Nettle at the Long Beach Aquarium.

• Cotylorhiza tuberculata
• Treatment of Coelenterate and Jellyfish Envenomations
• British Marine Life Study Society - Jellyfish Page
• Jellyfish - Curious creatures of the sea
• Sting treatment
• Jellyfish Grown with Twelve Heads
• Jellyfish Boom Driven Partly by Warming Waters

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