Portuguese Man O’War – Did You Know…

… That the Portuguese Man O’War is technically not a jellyfish?

Anyone unfamiliar with the biology of the venomous Portuguese man-of-war would likely mistake it for a jellyfish. Not only is it not a jellyfish, it’s not even an “it,” but a “they.” The Portuguese man-of-war is a siphonophore, an animal made up of a colony of organisms working together.

The man-of-war comprises four separate polyps. It gets its name from the uppermost polyp, a gas-filled bladder, or pneumatophore, which sits above the water and somewhat resembles an old warship at full sail. Man-of-wars are also known as bluebottles for the purple-blue color of their pneumatophores.

The tentacles are the man-of-war’s second organism. These long, thin tendrils can extend 165 feet (50 meters) in length below the surface, although 30 feet (10 meters) is more the average. They are covered in venom-filled nematocysts used to paralyze and kill fish and other small creatures. For humans, a man-of-war sting is excruciatingly painful, but rarely deadly. But beware—even dead man-of-wars washed up on shore can deliver a sting.

Muscles in the tentacles draw prey up to a polyp containing the gastrozooids or digestive organisms. A fourth polyp contains the reproductive organisms.

Man-of-wars are found, sometimes in groups of 1,000 or more, floating in warm waters throughout the world’s oceans. They have no independent means of propulsion and either drift on the currents or catch the wind with their pneumatophores. To avoid threats on the surface, they can deflate their air bags and briefly submerge.

The stinging, venom-filled nematocysts in the tentacles of the Portuguese man o’ war can paralyze small fish and other prey. Detached tentacles and dead specimens (including those that wash up on shore) can sting just as painfully as the live organism in the water and may remain potent for hours or even days after the death of the organism or the detachment of the tentacle.

Stings usually cause severe pain to humans, leaving whip-like, red welts on the skin that normally last two or three days after the initial sting, though the pain should subside after about 1 to 3 hours (depending on the biology of the person so stung). However, the venom can travel to the lymph nodes and may cause effects that mimic an allergic reaction including swelling of the larynx, airway blockage, cardiac distress, and an inability to breathe (though this is not due to a true “allergy”). Other symptoms can include fever and shock, and in some extreme cases even death, although this is extremely rare. Medical attention for those exposed to large numbers of tentacles may become necessary to relieve pain or open airways if the pain becomes excruciating or lasts for more than three hours, or breathing becomes difficult. Instances where the stings completely surround the trunk of a young child are among those which are potentially fatal.

Treatment of stings

Though often extremely painful, most stings from a Portuguese man o’ war do not require immediate medical treatment. The stings result in severe dermatitis characterized by long, thin open wounds that resemble those caused by a whip. These are not caused by any impact or cutting action, however, but by irritating urticariogenic substances in the tentacles. The usual round of treatment for a Portuguese man o’ war sting begins with the application of poured salt water to rinse away any remaining microscopic nematocysts—if the wound is rubbed or touched, this will cause the discharge of any nematocysts still attached to the skin; rinsing with salt water will help wash these “unfired” nematocysts away from the wound, though it will not directly relieve the pain (also, as this rinse water will likely contain some nematocysts, care should be taken to keep it from running over the victim’s skin: salt water poured down a leg may result in fresh stings suddenly appearing on the feet, for example). Fresh water has been shown to cause nematocystic discharge and is not recommended for this purpose.

Following rinsing with saltwater, the traditional next treatment step involves soaking the wound in acetic acid in a 5% solution (this is the proportion of acetic acid available in household vinegar) or in a solution of ammonia and water (3 parts water to one of ammonia). This is believed to deactivate the remaining nematocysts and will usually provide some relief from pain, though some isolated studies suggest that in some individuals vinegar dousing may increases toxin delivery and worsen symptoms. Vinegar has also been claimed to provoke hemorrhaging when used on the less severe stings of cnidocytes of smaller species, which is why the determination of the origin of the stings, if possible, is so important.

The vinegar or ammonia soak is then often followed by the application of shaving cream to the wound for 30 seconds, followed by shaving the area with a razor and rinsing the razor thoroughly between each stroke. This removes any remaining unfired nematocysts. Once shaved, the wound is then resoaked in either vinegar or ammonia. If available, heat in the form of hot salt water (not fresh) or hot packs is then applied at temperatures as hot as the victim can tolerate: heat speeds the breakdown of the toxins already in the skin. After a few hours, a thin layer of hydrocortisone cream at 1% concentration is applied. The victim must then be monitored over the next several days to see if the wound becomes infected: symptoms of infection such as fresh reddening of the wound’s edges, the production of pus, the development of a fever, the swelling or hardening of the lymph nodes nearest the wound, etc., indicate that the hydrocortisone is to be discontinued and professional medical treatment may then be necessary.

Isn’t it amazing what creatures are sharing this planet with us? And still we try to find new life in space when we have the most incredible and sometimes weird creatures right here…


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