How Do Sea Jellies Sting?

the science of cnidocytes and nematocysts

Sea jellies don’t sting through electricity or by touch. A sea jelly sting through a special type of cell called a Cnidocyte, there are three types of cnidocytes currently known. Spirocysts which entangle their prey, Ptychocysts which build tubes for tube anemones and the most well known Nematocysts. Nematocysts consist of a toxic barb which is coiled on a thread inside the cindocyte, when triggered the barb is ejected almost instantly taking only 700 nanoseconds to fire and firing with a force of five million g’s. A cindoctye can only fire once, and must be replaced when fired a process that could take 2 days.

Sea jellies 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 only some species’ venom cause 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 pounds per square inch (14,000 kPa) until it bursts. 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. Even beached and dying jellyfish can still sting when touched.

Scyphozoan jellyfish stings range from a twinge to tingling to agony. Most jellyfish stings are not deadly, but stings of some species of the class Cubozoa and the Box jellyfish, such as the famous and especially toxic Irukandji jellyfish, can be deadly. Stings may cause anaphylaxis, which can be fatal. Medical care may include administration of an antivenom.

Detailed Video of firing nematocysts

Jellyfish are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey.

Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal.

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