Deadly Portuguese Man O’ War Facts: Their Sting Can Kill You

With an odd appearance, the Portuguese man o’ war is a deadly yet fascinating marine creature in the ocean. It’s not an individual but many organisms. There are many more peculiar and intriguing facts about this unique and deadly species. 

Portuguese man o’ war
Scientific name: Physalia physalis
Phylum Cnidaria
Class Hydrozoa
Order: Siphonophora
Family: Physaliidae
Genus: Physalia

1. The Portuguese man o’ war is not a Jellyfish 

The Portuguese man o’ war, also known as man-of-war is a marine species. Despite their similarities in appearance, the Portuguese man o’ war is not a jellyfish. While they possess a “bell” and tentacles, they are siphonophores, which are colonial animals consisting of numerous genetically-identical organisms (known as polyps or zooid.)

A Portuguese man o' war is floating in the ocean

Because these particular creatures cannot exist alone, they have to join together as a group. Cooperation is necessary for activities such as moving and food acquisition.

In contrast, jellyfish are single organisms and not a combination of multiple individuals. 

Though both species are members of the phylum Cnidaria, man o’ wars are classified as Hydrozoa, whereas jellyfish belong to the Scyphozoa class. 

2. They’re made up 4 types of organisms

As mentioned above, the Portuguese man o’ war may give the impression of being an individual organism. It has no brain, heart, or gills. The species is actually composed of different zooids. It’s similar to a coral head which is comprised of multiple polyps. 

These zooids are mostly clones, but they come in varying shapes and have distinct functions. The man-of-war consists of four primary types of polyps, each with a specific role to play.

The first polyp, known as the pneumatophore, is a gas-filled structure that works as a huge bladder loaded with gasses like carbon monoxide. The bladder rests roughly 6 inches above the waterline and has a size of 5 inches in width and 2 inches in length. 

It is often translucent, with a tint of blue, purple, and pink. These hues let them blend in with the ocean waves. With the ability to contract or expand at its will, the float allows the man o’ war to maintain buoyancy. Furthermore, an expanded bladder lets the colony move fo with the wind. If you pop a man o’ war, there’s no more buoyancy and the species can die.

The remaining three types of polyps are gastrozooids, the tentacles responsible for feeding; dactylozooids, which protect the colony and capture prey with their larger and toxic tentacles; and gonozooids, whose function is to reproduce.

The expanded pneumatophore of the Portuguese man o’ war looks like a full-sail wooden ship used by the Portuguese navy in the 18th century. This type of ship was called a “man of war” by British sailors. This is how the marine species got its name. Additionally, the name may also have been influenced by the topped helmets worn by Portuguese soldiers in the 16th century.

3. Habitat

Portuguese man o’ wars are commonly spotted on the surface of warm tropical and subtropical waters worldwide. They live in the Caribbean, Atlantic Ocean, Indian Ocean, and Pacific Ocean. One of their preferred environments is the Sargasso Sea. Man o’ wars are not found in the Arctic Ocean.

The Indo-Pacific man o’ war is also called the bluebottle.

In the United States, they can be found on Florida’s Atlantic coast, Florida Keys, and Gulf of Mexico, extending to Texas. Occasionally, they even drift with the wind and currents, reaching as far north as Canada’s Bay of Fundy. They are also located in the coastal waters of Ireland and Britain.

They move to these places with only the help of winds and ocean currents and sometimes form groups of over 1,000.

4. Their Stings are painful, even death 

Like jellyfish, Portuguese man o’ war can sting. Long strings of tentacles lie beneath their bladder, growing up to 10 meters (30 feet) on average. Some of them can reach up to 50 meters (165 feet) – almost as tall as the Leaning Tower of Pisa.

These tentacles contain tightly packed stinging nematocysts that shoot out barbs when disturbed. The venom is deadly to small fish and crustaceans and can also hurt you. Even after the man-of-wars have died or lost their tentacles, they can still give you an excruciating sting.  

The tentacles of man-of-war

You can experience skin welts or perhaps some allergic reaction symptoms like vomiting, muscle cramps, and increased heart rates. Due to its painful sting, the man-of-war has earned the nickname the “floating terror.”

Although rare, a Portuguese man o’ war’s sting can kill you. In 1987, a person tragically suffered a complete cardiovascular collapse and passed away after encountering a man-of-war in eastern Florida. Recently, a woman swimming near Sardinia also died after being stung by a man-of-war.

Their sting on human

These weird creatures typically float in the open ocean and do not actively seek out human contact. However, it can occasionally be found in shallower coastal waters.  

If you are stung by a man o’ war, you can apply the sting treatment following the journal Toxins instruction. You can remove the tentacles and wash the affected area with vinegar to eliminate the remaining nematocysts. After that, soak the area in hot water, approximately 113 degrees Fahrenheit (45 degrees Celsius) for 45 minutes. You should get medical attention if the sting is really painful.  

5. They don’t look for food

The Portuguese man o’ war is a predatory organism that eats crustaceans, small fish and their larvae, worms, and plankton.

Unlike other carnivorous creatures, it doesn’t actively hunt for food. Rather, when the colony drifts, the prey is stuck and paralyzed in the deadly tendrils. Then, the prey is attached and dragged to the mouth by the feeding tentacles. This is similar to the way that By-the-wind sailors hunt.

Despite its venomous sting, the Portuguese man o’ war is not invincible and has several natural predators. They can be eaten by blue dragon sea slugs, violet sea snails, sea turtles, and crabs.

It is a common prey for both loggerhead turtles and ocean sunfish. These two species are also predators of jellyfish. Plastic bags in the water can often be mistaken for man-of-wars, making them an attractive target for turtles.

The Pacific sand crab is known to drag the man-of-war to shore and eat it with other crabs. The blue dragon sea slug consumes the man-of-war’s deadly nematocysts and keeps them in its finger-like cerata to use later. 

6. There are fish Live Among Its Tentacles 

The venomous man-of-war primarily feeds on fish, comprising 70 to 90 percent of their diet. Despite this, there is still a fish species that coexists among the siphonophore’s tentacles. It is the Portuguese man o’ war fish or bluebottle fish (Nomeus gronovii.)

Portuguese man o' war fish

In adulthood, this fish dwells near the ocean floor, but during its early stages, it resides amidst the lethal tentacles of man-of-wars. Unlike clownfish, these creatures lack immunity against the stings. Therefore, young bluebottle fish rely mainly on their agility to evade the nematocysts. 

The fish stay there to feed on small pelagic invertebrates that swim beneath the man-of-war. They will occasionally steal their host’s meal or munch on its tentacles as they grow older.

7. They have specific sex

Each colony of the Portuguese man o’ war contains sacs that house either ovaries or testes, making them either “male” or “female.” 

During the fall, they engage in sexual reproduction through broadcast spawning. This process involves large groups of man-of-war congregating, with females and males both discharging their eggs and sperm simultaneously into the water column at the same time for fertilization. 

A group of Portuguese man o' war gather together
Man O’ War reproduce

A siphonophore develops from a fertilized egg and forms separate structures and organisms through a process called “budding.” These structures, called polyps or zooids merge together into a complete species.

The average lifespan of a Portuguese man o’ war is estimated to be at least one year, varying with water temperature and conditions.

8. They go with the flow 

The Portugese man o’ war thrives exclusively in the open ocean. It relies on wind and currents to drift on the surface, aided by its large float. This locomotion style makes it prone to washing up on beaches across the globe, from South Carolina to Britain to Australia.

Man O’ War dead on the beach

When generating new colonies, the man-of-war’s floats tilt either left or right, enabling them to disperse in various directions and distribute themselves more widely across the ocean.

If the species detects a threat on the surface, it can briefly deflate its pneumatophore and drop below the water. The species also uses this technique to avoid dehydration.

9. Conservation Status

At present, the Portuguese man o’ war is not on the list of endangered species. The warming of the ocean due to global warming is causing a decrease in oxygen levels in the water, which is harmful to various marine creatures. Surprisingly, this has led to a conducive environment for jellyfish and the man-of-war to thrive.

With the continuing rise in ocean temperatures, their colonies will expand and spread across Canada and northern regions. However, global warming will decrease their primary source of food, like fish.  



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