Portuguese Man O’ War (Physalia utriculus)

These beautiful creatures are commonly thought of as common Jellyfish; however, they are actually far more complex. Man o’ wars are composed of multiple organisms all working together!

Blue bottle jelly - Image Source: BBC & NatGeo


The Blue Bottle man o’ war is actually what is called a siphonophore. Siphonophores are a colony of specialized minute individual organisms called zooids. These zooids share tissue and cannot survive independently.

Zooid Close-up: Image Courtey: Aaron Ansarov

The man o’ war has no means of propulsion, but has an air sack that keeps it near the surface where winds, tides and currents propel it around the Atlantic Ocean. They spend the majority of their time at the surface, but can submerge by deflating their air sack if attacked.

Deadly Sting

The man o’ war has a deadly sting. Their tentacles are composed of hundreds of bands of stinging cells. Some cells are specialized to feed while others for defense and stunning prey. They can be deadly to humans depending on where one is stung. A hand sting for most adults will be painful, but not deadly in most cases. A sting on thin-skinned areas of the body, however, is potentially fatal.

Video Source: National Geographic

That said, ten thousand people are stung each summer by the man o’ war in Australia alone but deaths are rare. Detached stingers and/or a dead organism’s stingers can be just as painful as the living organisms, so walking barefoot on a beach covered in them is not a good idea.

Woman walking along the jellies - Image Source: Shutterstock


Several organisms prey on the man o’ war including the loggerhead turtle, the ocean sunfish, the violet snail, and a few sea slug species (like the Blue Glaucus below).

Glaucus atlanticus - Image Courtesy: The Conservation


Learn more about the man o’ war by checking out our friends at Sci-Show, below:

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