Jellyfish? Man or woman? Some facts about Portuguese Man of War Edit

Ever since the first death by a Portuguese Man of War has been reported in the Mediterranean in 2010 (in Sardinia) more and more people especially in the med got curious about this jellyfish.  Ah no, first misconception, the Portuguese Man of War is not a jellyfish but rather a marine phylum, it differs from a jellyfish in so far as it is not actually a single multicellular organism but a colonial organism made up of many highly specialized minute individuals called zooids.

Physalia physalis

It lends its name from the 18th-century warship man-of-war, and the phylum’s supposed resemblance to the Portuguese version at full sail. In Australia it is known as bluebottle for its gas-filled bladder that is seen at the ocean service.

We call it “man” but the Portuguese man of war has no gender it is dioecious, its gametes are released into the sea and then fertilized externally, fertilised eggs then undergo gastrulation.

Is it lethal? Well there are few deaths attributed to the Portuguese man of war and only one in the Mediterranean.  Potentially these deaths relate to a severe allergic reaction to the venom.  However they do sting tremendously and cause severe pain.

If stung, do not treat like a jellyfish, that is pour vinegar on the sting as this makes it worse.  Rather apply salt water to the affected area (not fresh water, which tends to make the affected area worse) and follow up with the application of hot water (45°C) to the affected area from 15 to 20 minutes, which eases the pain of a sting by denaturing the toxins.

Since the Portuguese man o’ war has no means of propulsion, it is moved by a combination of winds, currents, and tides. Although it can be found anywhere in the open ocean (especially warm water seas), it is most commonly found in the tropical and subtropical regions of the Pacific, Indian and Atlantic oceans. However we now see it more in the Mediterranean due to the changes in sea temperature.


Slaughter RJ, Beasley DM, Lambie BS, Schep LJ (2009). “New Zealand’s venomous creatures”. N. Z. Med. J. 122 (1290): 83–97.

Yoshimoto, C.M., and Yanagihara, A.A. Cnidarian (coelenterate) envenomations in Hawai’i improve following heat application. Transactions of the Royal Society for Tropical Medicine and Hygiene 96, 300–303, 2002.