Stinging Cells--What Makes the Cnidarians What They Are!

Like their Cnidarian cousins (the corals, sea anemones, and hydra), jellyfish's main claim to fame are the microscopic stinging cells that coat their tentacles (tendrils or "oral arms") that extend from their main body (their "bell"). These cells, called cnidocytes, contain a specialized organelle called a cnidocyst or nematocyst that holds a barbed venom capsule. When the stinging cell is triggered, the nematocyst fires in a discharge that is one of the fastest biological processes--as fast as 600 nanoseconds an acceleration approaching five-million g. After penetration, the nematocyst injects the neurotoxic venom into the targeted organism (fish and crustaceans--sometimes planktonic), which immediately paralyzes the organism--allowing the jellyfish to either pull it to its oral cavity ("mouth") to eat it or to release it to escape from it.

Jellyfish do not actively seek out and attack their prey, but rather, float mostly transparently and unseen by their unsuspecting prey that inadvertently ventures into contact with their tentacles and the subsequent firing of the stinging cells.

A dangerous things about the cnidocytes and nematocytes is that they can fire independently. The animal can be considered "dead", yet the stinging cells can still deliver a nasty sting.

I experienced this hazard first-hand when I lived on Guam. Occasionally, especially after typhoons, jellyfish and Portuguese Man-o-War would wash up on the beaches around the island. One clear day after such a storm, I was walking along the beach to see what had washed up from the storm. For amusement, I used a stick to turn over rocks to see what was under them and to pop the inflated "sails" of the Portuguese Man-o-War that were laying shriveled and dried along the shore. I did this for about an hour before returning to the road that led to my home. As I walked back home, some mosquitos and other insects tried to get their dinner off my back. I instinctively and reflexively used the stick to scratch my back. Wrong move!--the stick was now entangled with the remains of the tentacles of Portuguese Man-o-War that I had been poking earlier. The moment I touched my back with the stick, an intense pain rose on my back. It was then that I realized what I had done. I dropped the stick and ran home--where my Dad helped with pulling and scraping the stingers and tentacle pieces off my back and making a sauve of baking soda that he smeared on the wounds. I had some nasty and painful sores on my back for quite a while.

The most deadly cnidocytes (to humans, at least) are those of the box jellyfish (which is not a true jellyfish--but a close relative). One member of this phylum of the Cubozoa class, the sea wasp, Chironex fleckeri, is the one of the most venomous marine animals known. It causes excruciating pain, followed by death, sometimes within two or three minutes. The chance of survival if stung while swimming alone is "virtually zero." Another infamous and potentially deadly Cubozoan (box jelly) is the Irukandji--a thumbnail-sized jellyfish (Carukia barnesi) that lives mostly off the coast of Australia. The Irukandji is unique among jellyfish in that it not only has stinging cells on its tentacles, but it also has stinging cells on its bell. The venom is injected only from the tip of the stingers rather than from the entire length--resulting in a sting that is initially mild but with a delayed reaction that can be deadly.

Other cnidarians, such as the "lion's mane" jellyfish Cyanea capillata (made famous in Sir Arthur Conan Doyle's Sherlock Holmes story, "The Adventure of the Lion's Mane") or the hydrozoan Physalia physalis (Portuguese Man o' War, "Bluebottle") can cause extremely painful and sometimes fatal stings.

First Aid for Jellyfish Stings

Though most jellyfish stings are not deadly, some stings, such as those of the box jellyfish (Chironex fleckeri), are frequently fatal. Serious stings may quickly cause anaphylaxis and paralysis. Therefore, those stung by jellyfish must quickly 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.

Three immediate actions required for uncomplicated jellyfish stings:

• prevent injury to rescuers (using barrier clothing--panty hose, wet suits, blue-jeans, full-body sting-proof suits)


• inactivate the nematocysts (to prevent further venom injection into the victim)
• remove any tentacles stuck on the patient

Vinegar (3 to 10% aqueous acetic acid) should be applied for box jellyfish stings. However, vinegar is not recommended for Portuguese Man o' War stings. 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. 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. DO NOT RUB THE WOUND. DO NOT USE ALCOHOL, AMMONIA, OR URINE BECAUSE THESE WILL ENCOURAGE RELEASE OF MORE VENOM.

Once deactivated, the stinging cells must be removed by picking off the tentacles left on the victim's body. Use gloves or another readily available barrier device to prevent personal injury. After the large pieces of jellyfish are removed, shaving cream may be applied to the area and a knife edge, safety razor, or credit card may be used to remove any remaining nematocysts.

Beyond initial first aid, antihistamines such as diphenhydramine (Benadryl) may be used to control skin irritation (pruritus). 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.

Jellyfish are an important source of food in many Asian countries. Only jellyfish belonging to the order Rhizostomeae (especially Rhopilema esculentum, Mandarin name: haizhe) are harvested for food because they are typically larger, have no tentacles or stinging cells, and have more rigid bodies than other jellyfish.

Traditional processing methods involve a mixture of table salt and alum, and then desalting, which makes the jellyfish drier and more acidic. Jellyfish prepared this way are about 95% water and 4 to 5% protein, making it a relatively low calorie food.

After trying some when I visited Taiwan and then later when in Japan, I realized that it's sort of an "acquired taste".... to me they taste like dried rubber bands. The addition of soy sauce improves their taste a bit, but not much. However, your mileage may vary--give them a try the next time you visit a Chinese restaurant!