Jellyfish inject their venom by way of the many tentacles dangling from their bell, or bodies. The box jelly, which gets its name from the boxy shape of its bell, has 4 tentacles, each of which contains about 5,000 stinging nematocysts, housed in cells called cnidoblasts. Nematocysts are like little stinging darts that fire whenever the tentacle comes in contact with chemicals on the surface of its prey. A single encounter with a jellyfish can leave you with thousands of stings, and the powerful venom doesn't waste any time getting to work. Many victims stung at sea, go into shock or die of heart failure before they can even reach the shore.Not only is jellyfish venom damaging to the heart, muscles and nervous system, it's also dermonecrotic, meaning it's capable of killing skin cells and underlying tissue, leaving you with dead, blackened skin and potentially permanent scarring. Some jelly venom even breaks down blood cells. To make matters worse, your initial instinct to shake the offending stingers off makes the tentacles contract and stick tighter to your skin, potentially releasing even more stingers into your already burning flesh.How do you get Stung?Each cnidocyte cell contains a nematocyst; which comprises a bulb-shape capsule containing a coiled hollow thread-like structure attached to it. The outward facing side of the cnidocyte has a hair-like trigger called a cnidocil, when the trigger is activated (usually on contact with a skin protein), the shaft of the cnidocyst penetrates the target organism, and the hollow thread is everted into it. This process happens incredibly quickly and with a surprising amount of force.
Structure of a nematocyst:The cnidocyte capsule stores a large concentration of calcium ions, which are released from the capsule into the cytoplasm (the stuff inside the cell excluding organelles) of the cnidocyte when the trigger is activated. This increase of calcium literally forces water to be drawn in to the capsule which pushes onto the nematocyst and causes it to eject rapidly. The coiled nematocyst is a hollow tube that exists inside the cell in an 'inside out' condition. The pressure of water flowing into the cnidocyte forces the water into the tubular nematocyst causing it to right itself as it comes rushing out of the cell with enough force to impale a prey organism.
This discharge takes no more than a few microseconds, and is able to reach accelerations of about 40,000 g (g – referring to gravitational force). Recent research suggests the process occurs as fast as 700 nanoseconds, and the thread reaches an acceleration of up to 5,410,000 g. This is amazing as humans typically pass out at 9 g’s and fighter pilots ejection seat fire with 32 g’s. In fact the highest gravitational force a human has ever survived was 178 g by a British Formula One racer, David Purley, who crashed in 1977, his car going from 173 km/h to 0 in only 66 cm (which basically means he hit a wall and the car structure compressed to decelerate him). He broke many bones, but survived and this deceleration of his, is believed to be the highest ever survived by a human being. The closest human experience of a nematocyst firing is if our skin was the outside of an aircraft and the nematocysts was a missile... I’ll leave the rest to your imagination...
Cnidocytes can only fire once; used cnidocytes have to be replaced, which takes about 48 hours. To minimise wasteful firing, two types of stimulus are generally required to trigger cnidocytes: cilia (hair) in mechanoreceptors (cells which detect vibrations) contact, and nearby sensory cells which 'smell' chemicals (usually skin proteins) in the water. This combination prevents them from firing at distant or non-living objects. Australian lifeguards used to wear women’s pantyhose to protect them from being stung, as although they would brush past a jelly nematocyst, the nematocyst couldn’t smell their skin and thus wouldn’t fire. Thankfully theses days lifeguards look more manly thanks to the invention of lycra full body swim suits. Some jellies and anemones are even more sophisticated with their mechanoreceptors tuned to specific vibration frequencies such as the swimming motion of its prey. It’s thought that this is the reason why you can touch an anemone, rather than sting you and waste its cnidocytes, it will withdraw its tentacles into its body. Groups of cnidocytes are usually connected by nerves and if one fires, the rest of the group requires a weaker minimum stimulus than the cells that fire first.It is possible to get stung even while wearing a wet suit although usually this happens as you remove the wet suit and drag it over your skin. The wet suit will have skin cells that have rubbed off you and become stuck to the wetsuit. Some of the nematocysts may fire and anchor the tentacle into the suit as they smelt the skin cells. You may not see the tentacle but you can become stung as you are removing the suit, even if the suit has been drying in the sun. This is because nematocyst can fire independently from a nerve impulse and even several weeks after being on the suit (ask me I know!).Why is it so hard to get the tentacles off you?There are actually 2 forces which help to attach the tentacles to prey: 1) adhesion of the nematocyst capsule to the tentacle 2) the stickiness of mucus covering the tentacle and in sea anemones (which are related to jellyfish) a third force exists 3) adhesion of the nematocyst threads from specialized cells called spirocysts, to the prey.
Tentacles are designed to stick so they can be incredibly difficult to remove. The best way is to use gloves and a credit card and scrape them off the skin.Flushing the area with water and rubbing sand can actually cause more tentacles to fire.
How is their venom delivered?There are three types of venom which will be injected into you when you are envenomated by a nematocyst. On the outside of the dart is capsular plaque. Inside the dart which is essentially a hollow tube, is tubular matrix. Inside the nematocyst is capsular matrix. As the coiled tube is being fired it twists and everts and has a motion similar to that of a drill. The spines will appear and help to anchor the nematocyst to you. During the twisting motion the capsular plaque and the tubular matrix is released into your skin surrounding the dart. Studies have shown that the tubular matrix causes blood cells to breakdown. As the nematocyst is still under pressure the capsular matrix is forced through the dart to the tip, once it has reached the end of the dart it will burst the dart and the poison will be expelled into your body in small drops.
As symptoms are very rapid following a sting, some of the venom is delivered directly into your blood stream. Some nematocysts are capable of firing to a depth of more than 550 um, which would place the tip of the shaft deep into your skin tissue. Due to the large number of nematocysts that fire during a sting, it is possible that some of the capsular matrix can be introduced directly into the blood stream. This coupled with the tubular matrix which, is being released all the way down the shaft will result in very rapid cardiovascular effects as well as resulting in massive skin death. In most cases however, the bulk of all three matrices pass into extra-vascular spaces and this will result in the skin pain, skin damage and acute inflammatory response at the sting site.
Thankfully there's somewhat of a cure, if you can get to it fast enough! Acetic acid solutions like vinegar have been shown to render ONLY the stinging cells in box jellies, harmless, preventing them from firing more toxins into your body. (Antivenin is also available.)The best treatment is hot water (as hot as you can stand without burning yourself), followed by cold packs and constant monitoring for anaphylactic shock. Or you could do what some savvy Aussies do, and wear women's pantyhose when you head out to the beach.
The juice of the sour fig leaves have traditionally been used as an antiseptic. It is also thought to be effective for jellyfish stings when applied liberally to effected areas to help soothe the itch and aid in healing. With a jelly fish sting the bulk of the injury will be a penetration injury on the surface of the skin and the juice of the sour fig may aid in decreasing the symptoms. However saying that, if after using it you get any of the following: Severe pain, high swelling, breathing problems, or difficulty swallowing. These are major symptoms that occur in those who suffer from severe allergic reactions to jellyfish stings.If this is the case, forgo any homemade treatments and SEE A DOCTOR IMMEDIATELY.There are several home remedies for jelly stings ranging from, vinegar, to urine to baking soda.The best is hot water (as hot as you can stand without burning yourself) followed by a cold compress and antihistamines.As on some species of jelly fish some of the home remedies mentioned below can actually increase the number of nematocysts that fire and can make the sting worse.Other house wife remedies include:Vinegar – By sprinkling vinegar liberally around the sting its thought to deactivate the nematocysts that are chiefly responsible for the classic pain and itch of blue bottle and box stings. This remedy should ONLY be used for blue bottles and box jellies. White distilled vinegar, and apple cider vinegar, seem to work best . I can just imagine my mom running to the kitchen panty when on holiday and bringing out all the different types of vinegar to see which works best.Urine - The old wives’ tale that sprinkling urine on the wound has been around for years, but remains a highly debatable option among the professional medical community. In fact ureic acid actually causes more compass jelly nematocysts to fire and although research studies have not proven its effectiveness against the pain of jellyfish stings, there's enough anecdotal evidence that says it really works. (I personally think that you will say anything to stop someone from peeing on you. But if you're stuck at the beach, it's a lot easier to produce than a bottle of vinegar.)Baking soda - The classic Atlantic shore home remedy said to be especially effective against common stinging nettle jellyfish. Simply mix 3 teaspoons of baking soda with 1 teaspoon of salt water until a thick paste forms, and apply. Mix with salt water only. Fresh water tends to activate the toxins.Other remedies’ include:Unseasoned meat tenderizerHousehold ammoniaLemon or lime juiceAfter applying your homemade cure, inspect the area around the wound and remove the stingers. Experts (read house wives tales) say the easiest way to do this is to cover the area with shaving cream and scrape with a safety razor. If you're at the beach, using a shell or credit card to scrape away the stinging cells will work, NOT your hands and fingers as this will results in you also getting stung.To assist with pain relief you can try the following:Pain relievers - Simple aspirin, ibuprofen, or acetaminophen will help keep the pain to manageable levels and help you get some sleep.Hydrocortisone cream - Quick over-the-counter relief for painful itching and swelling. 
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