Dr. Özgür Deniz Tezcan
The Phylum Cnidaria consists of about 10,000 species of animals. Common jellyfish, anemones, corals, sea pens, cube shaped jellyfish all cnidaria with diverse morphology. Cnidaria is characterized by cells called nematocytes (cnidocyte). These cells secrete a very special organelle called nematocyst (cnidocyst). Cnidocyst, sine qua non of cnidaria is used for defense and prey. Inside the cnidocyst, there is an inverted tubule, venom and a huge osmotic pressure. 150 bars. This pressure is comparable to the pressure of a scuba cylinder. When the cnidocyst is triggered, the inverted tubule coiled inside the cnidocyst is everted and ejected with an enormous acceleration. 5.5g. This acceleration is ten times more than a 9mm bullet shot out of a Beretta gun. The tip of the tubule may be as sharp as 80 nm2, i.e. as the diameter of four DNA strands. Together with the speed and sharp tip, it can produce 7.7 GPa pressure at the point of contact. This pressure is higher than the pressure required to produce artificial diamond from graphite.
General information about first aid
The first aid against cnidaria envenomations consists of preventing further nematocyst discharges, alleviating the local effects and controlling systemic reactions. In case of contact with jellyfish generally the tentacles stay attached to the skin and a significant amount of nematocysts are not activated. The nematocysts are sensitive to osmotic changes (like fresh water application) or tactile stimuli (like rubbing). Therefore, it is important to avoid further nematocyst discharge and to remove all the unfired nematocysts as soon as possible.
The safest way to get rid of the unfired nematocysts is to rinse away the sting area by sea water. Remaining tentacles could also be removed by scrubbing the skin by a credit card or dull edge of a knife or detaching by tweezers. Pressure (rubbing, scratching, itching etc.) or rinsing by fresh water, alcohol, methylated spirits should be avoided.
Some chemicals have been shown to stabilize unfired nematocysts so they cannot inject venom. Among them, 5% acetic acid (vinegar) can effectively neutralize the nematocysts of Chironex fleckeri. So, in the first aid of Box jellyfish (class Cubozoa) stings, vinegar application, has taken place as a part of the standard treatment.
But there are conflicting reports about the effectiveness of vinegar for other Cnidarian stings. It has been shown that vinegar trigger the nematocysts of Physalia sp., Pelagia noctiluca, Lytocarpus philippinus and Cyanea capillata. So, most sources recommend vinegar application only to stings from the box jellyfish. One of the more recent promising chemical to stabilize unfired nematocysts could be %1 lidocaine.
Most jellyfish envenomations are mild. They cause slight discomfort or a painful, itchy rash. Although rare, some systemic reactions may be seen like hypotension, hypertension, shock, anaphylaxis, blurred vision, acute renal failure, fulminant hepatitis, autonomous nervous system disturbances, Guillain Barre syndrome, stroke, peripheric neuropathy, etc. The patient should be followed for a probable systemic reaction. The most effective and safe first aid to control the pain is hot sea water immersion. Hot water (43–45°C) immersion of the affected area for 20-40 minutes will ease the pain in most cases. If no thermometer is available, hot water immersion can be applied as hot as can be tolerated.