Culinary uses
Only scyphozoan jellyfish belonging to the order Rhizostomeae are harvested for food; about 12 of the approximately 85 species are harvested and sold on international markets. Most of the harvest takes place in southeast Asia. Rhizostomes, especially ''Rhopilema esculentum'' in China (Chinese name: ''hǎizhē'', meaning "sea sting") and ''Stomolophus meleagris'' (cannonball jellyfish) in the United States, are favored because of their larger and more rigid bodies and because their toxins are harmless to humans.Traditional processing methods, carried out by a Jellyfish Master, involve a 20 to 40 day multi-phase procedure in which after removing the gonads and mucous membranes, the umbrella and oral arms are treated with a mixture of table salt and alum, and compressed. Processing reduces liquidation, off-odors and the growth of spoilage organisms, and makes the jellyfish drier and more acidic, producing a "crunchy and crispy texture." Jellyfish prepared this way retain 7-10% of their original weight, and the processed product contains approximately 94% water and 6% protein. Freshly processed jellyfish has a white, creamy color and turns yellow or brown during prolonged storage.
In China, processed jellyfish are desalted by soaking in water overnight and eaten cooked or raw. The dish is often served shredded with a dressing of oil, soy sauce, vinegar and sugar, or as a salad with vegetables. In Japan, cured jellyfish are rinsed, cut into strips and served with vinegar as an appetizer. Desalted, ready-to-eat products are also available.
Fisheries have begun harvesting the American cannonball jellyfish, S''tomolophus meleagris'', along the southern Atlantic coast of the United States and in the Gulf of Mexico for export to Asia.
In biotechnology
In 1961, Osamu Shimomura of Princeton University extracted green fluorescent protein (GFP) and another bioluminescent protein, called aequorin, from the large and abundant hydromedusa ''Aequorea victoria'', while studying photoproteins that cause bioluminescence by this species of jellyfish. Three decades later, Douglas Prasher, a post-doctoral scientist at Woods Hole Oceanographic Institution, sequenced and cloned the gene for GFP. Martin Chalfie of Columbia University soon figured out how to use GFP as a fluorescent marker of genes inserted into other cells or organisms. Roger Tsien of University of California, San Diego, later chemically manipulated GFP in order to get other colors of fluorescence to use as markers. In 2008, Shimomura, Chalfie, and Tsien won the Nobel Prize in Chemistry for their work with GFP.Man-made GFP is now commonly used as a fluorescent tag to show which cells or tissues express specific genes. The genetic engineering technique fuses the gene of interest to the GFP gene. 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 turns on in the same tissues and the same time as the normal gene. But instead of making the normal protein, the gene makes GFP. One can then find out what tissues express that protein—or at what stage of development—by shining light on the animal or cell and observing fluorescence. The fluorescence shows where the gene is expressed.
Jellyfish are also harvested for their collagen, which can be used for a variety of applications including the treatment of rheumatoid arthritis.
In captivity
Jellyfish are displayed in aquariums in many countries. Often the tank's background is blue and the animals are illuminated by side light, increasing the contrast between the animal and the background. In natural conditions, many jellies are so transparent that they are nearly invisible.Jellyfish are not adapted to closed spaces. They depend on currents to transport them from place to place. 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. Jellyfish are becoming a popular trend in home aquariums. It is now possible to buy jellyfish aquariums and live jellyfish online. It is also possible to assemble a jellyfish aquarium for personal use.
Toxicity to humans
All jellyfish sting their prey using nematocysts, also called cnidocysts, stinging structures located in specialized cells called cnidocytes, which are characteristic of all Cnidaria. Contact with a jellyfish tentacle can trigger millions of nematocysts to pierce the skin and inject venom, yet the sting of only some jellyfish species causes an adverse reaction in humans. When a nematocyst is triggered by contact by predator or prey, pressure builds up rapidly inside it up to 2,000& lbs/sq. inch until it bursts open. A lance inside the nematocyst pierces the victim's skin, and poison flows through into the victim. Touching or being touched by a jellyfish can be very uncomfortable, sometimes requiring medical assistance; sting effects range from no effect to extreme pain to death. Because of the wide variation in response to jellyfish stings, it is wisest not to contact any jellyfish with bare skin. Even beached and dying jellyfish can still sting when touched.Scyphozoan jellyfish stings are often uncomfortable, though not generally deadly, but some species of the class ''Cubozoa'', or the Box jellyfish, such as the famous and especially toxic Irukandji, can be deadly. Stings may cause anaphylaxis, which may result in death. Hence, victims should immediately get out of the water. Medical care may include administration of an antivenom.
The three goals of first aid for uncomplicated jellyfish stings involve preventing injury to rescuers, deactivating the nematocysts, and removing tentacles attached to the patient. Rescuers should wear barrier clothing, such as panty hose, wet suits or full-body sting-proof suits. Deactivating the nematocysts, or stinging cells, prevents further injection of venom.
Vinegar (3 to 10% aqueous acetic acid)is a common remedy to help with box jellyfish stings, but not the stings of the Portuguese Man o' War (which is not a true jellyfish, but a colony). For stings on or around the eyes, a towel dampened with vinegar is used to dab around the eyes, with care taken to avoid the eyeballs. Salt water is also used if vinegar is unavailable. Fresh water is not used if the sting occurrs in salt water, as changes in tonicity can release additional venom. Rubbing wounds, or using alcohol, spirits, ammonia, or urine have strongly negative effects as these also encourage the release of venom.
Clearing the area of jelly, tentacles, and wetness further reduces nematocyst firing. Shaving the affected skin with a knife edge, safety razor, or credit card can remove remaining nematocysts.
Beyond initial first aid, antihistamines such as diphenhydramine (Benadryl) can control skin irritation (pruritus). For removal of venom in the skin, a paste of baking soda and water can be applied with a cloth covering on the sting. In some cases it is necessary to reapply paste every 15–20 minutes. Ice or fresh water is not be applied to the sting, as this may help the nematocysts to continue releasing their toxin.
In 2010 at a New Hampshire beach, pieces of a single dead lion's mane jellyfish stung between 125 and 150 people.
Adapted from the Wikipedia article Jellyfish, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki
