Marine Sciences & One Health

Portuguese Man O’ War Spotted On Galveston Beaches

Over the last several weeks, local social media groups have seen an influx of questions about the appearance of balloon-like creatures on Galveston area beaches. These animals are known as the Portuguese man o’ war (Physalia physalis).

“Rather than a jellyfish, Portuguese man o’ war are a colony of polyps,” said Dr. Maria Miglietta, an associate professor in the marine biology department at Texas A&M University at Galveston whose research specializes in Cnidarians, a group of animals that includes other species such as jellyfish, corals and sea anemones. 

The Portuguese man o’ war is a siphonophore, a colonial organism made up of numerous specialized individuals, or polyps, that work together to function as a single unit. Portuguese man o’ war belong to a class of organisms known as the Hydrozoans, a type of Cnidarian.

Named for their striking resemblance to the 18th century warship, the Portuguese man o’ war is typically found in the warm waters of the Atlantic Ocean and Gulf Coast waters. These sightings, while not uncommon, tend to increase during hurricane season in the Gulf. They are often brought to shore by strong winds, currents or storms, resulting in large numbers of these creatures being stranded along the shoreline. 

The most recognizable part of the Portuguese man o’ war is its translucent, balloon-like float called a pneumatophore, which is filled with air to allow the creature to stay afloat and drift across the water’s surface using either the wind or ocean currents, as it is incapable of swimming on its own.

Below the creature’s float are dangerous tentacles, which can extend up to 30 feet in length. These tentacles are lined with specialized stinging cells, called nematocysts, that release venom when triggered to trap small marine life as prey. This venom can cause a painful reaction in humans. What makes these creatures particularly hazardous for beachgoers is that their nematocysts can remain active and cause pain long after the man o’ war has washed ashore and has perished.

Galveston Island Beach Patrol urges beachgoers to use caution when encountering the Portuguese man o’ war, and if you happen to come in contact with the tentacles to douse the area with a saline solution and avoid rubbing the area as it will cause any remaining nematocysts to release venom.