Sealife guideThe portuguese man o' warPhysalia physalis

Last updated on 09/03/2025 at 11:26 PM

With its gelatinous body and tentacles, the Portuguese man o' war is not actually a jellyfish despite appearances, but rather a hydrozoan !

The Portuguese man o' war is commonly called by that name because of its resemblance to Portuguese sailing ships from the Middle Ages, but it is also known as the bluebottle due to its bladder-shaped body that floats on the ocean surface.

Taxonomy

Common name: Portuguese man o' war, Portuguese man of war
French name: Galère portugaise, physalie, vessie de mer
Scientific name: Physalia physalis (Linnaeus, 1758)
Family name: Physaliidae
Order name: Siphonophorae
Class name: The hydrozoans [Hydrozoa]

Habitat

The Portuguese man o' war is a marine species that drifts at the surface of seas and oceans with winds and currents.

The portuguese man o' war (Physalia physalis) © Aldorado10 | Dreamstime.com

Reproduction

The Portuguese man o' war is hermaphroditic and reproduces sexually in spring and summer. Male and female gametes are released into the seawater where fertilization occurs. The resulting larvae are planktonic and eventually develop into adult colonies.

Did you know ?

The venomous tentacles of the Portuguese man o' war can break off and drift independently. Detached tentacles are even more dangerous, since without the floating body they provide no warning signal for nearby swimmers.

Contact with a Portuguese man o' war causes immediate and very painful skin lesions similar to burns or hives.

Later, more severe symptoms may appear, such as dizziness, fainting, rapid heart rate and high blood pressure, abdominal or muscle pain, difficulty breathing, vomiting or fever.

Tips for observing

Never touch a Portuguese man o' war, even one washed up dead on the beach, as its stinging power remains intact !

Discover also

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(Rhizostoma pulmo)

Big siphonophore
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Bladed fire coral
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Staghorn coral
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