Invasion of the Portuguese Man of War

Two jellyfish laying on the ground next to each other.

Invasion of the Portuguese Man of War

This past weekend we’ve seen some reports of some Portuguese Man of War washing up on Tybee’s beach.  They look like small (4-6 inch) oblong blue balloons with a tangled mass of short tentacles hanging from below.  I had been hearing recently of some washing up on Jacksonville and St. Augustine beach, and with the consistent winds from the south this week, I was afraid that we might see some also.

Although often considered as a kind of jellyfish, a Man of War is actually a “colony” of individuals living together and forming a single animal.  The blue float is one type of individual, and 3 other types (for feeding, defense, and reproduction) form the mass of tentacle-like strings below.  The defensive tentacles, that can be 60 ft or longer, cause the powerful stings that the Man of War is known for.

They get their name from the large blue float that apparently resembled the Portuguese sailing ships of the past.  Along the top of that float is a ruffled ridge that is slightly off-kilter to the right or left; and as the wind blows them, they will “sail” to either the right or left of the direction of the wind.  So as our group of invaders was getting blown ashore recently, about the same number were being blown off shore or along shore.  For the most part, the Portuguese Man of War is a tropical, pelagic (open ocean) species; but when the winds and currents are just right, numbers of them can be driven long distances and onto shorelines.

Photo by Tybee Island Marine Science Center

Although they look harmless on the beach, the tentacles can still deliver a powerful sting, so it is best not to handle them.  Many different treatments for Man of War sting have been tried and studied, and most studies have found variable and even conflicting results. So the most common recommendation is to carefully remove any remaining tentacles that might still be on the skin; but use a towel or something so that you don’t get stung when removing them. And then rinse the area with seawater.  You can try something like lidocaine or hydrocortisone or benadryl cream, but realize that the sting will last for a while.  Some folks have allergic reactions, so be on the lookout for these symptoms, and treat them as an emergency.

The one good thing about Portuguese Man of War is that they float on top of the water, so you can see them coming.  But the tentacles can be spread out in the water for quite a distance.  So if you see one approaching or floating nearby, give it plenty of room.

Dr. Joe Richardson (Ph.D. Marine Sciences) has studied marine life along Tybee Island for more than 35 years, and he leads his Tybee Beach Ecology Trips for families, schools and other groups year-round at Tybee Island. and on facebook: Tybee Beach Ecology Trips.

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