Featured Creature: Portuguese Man O’War

"Portuguese man o' war" by 4Neus is licensed under CC BY 2.0.

Which creature is composed of four organisms in a symbiotic relationship, floats across the ocean because it lacks propellers, and stings prey with venom-producing tentacles?

The Portuguese Man O’War!

“Portuguese man o’ war” by 4Neus is licensed under CC BY 2.0.

Last weekend, during a conversation on a camping trip up in the Berkshire mountains, one of my friends shared how he had learned about a creature called the Portuguese Man O’War, which happens to be multiple organisms existing in a single, specific, symbiotic relationship. Fascinated, I jotted down the name and got straight to researching them when I returned home. The more I learned, the more I got excited about this unique species and immediately knew they were Featured Creature material. 

Totally Tubular

One of the most key points to know about the Portuguese Man O’War is that it is a siphonophore. This means that they are a colony of organisms (called zooids) that interact in a symbiotic relationship. While the Portuguese Man O’War is often considered a member of the jellyfish family, their special status as a siphonophore sets it apart from the rest. 

Relatively tubular in shape and transparent with blue, pink, and/or purple tint, the Portuguese Man O’War is made up of four different zooids (a.k.a an organism that is part of a larger colony): the pneumatophore, the dactylozooids, the gastrozooids, and the gonozooids. The pneumatophore is the balloon-like structure that is visible above the water line. It is filled with atmospheric gasses, primarily carbon monoxide. The dactylozooids are tentacles filled with venom-filled nematocysts – they sting predators and capture prey. The gastrozooids are tentacles that digest food and nutrients coming into the organism. Lastly, the gonozooids are tentacles that serve a reproductive function. 

A Worldy Creature

Contrary to what you may initially think, the Portuguese Man O’War (also known as Physalia physalis) is not native to Portugal. They can be found in the Indian Ocean, the Pacific Ocean, the Atlantic Ocean, and even the Caribbean Sea. “So, where does the name come from?” you might be asking. Well, some believe that the fan-like shape of the pneumatophore looks like the sails on a Portuguese Navy ship from the 1700s. 

Illustration By Thomas Luny In The Public Domain Via Florida Museum 

They enjoy living in tropical or subtropical climates in coastal and open-ocean environments. As a carnivore, the Portuguese Man O’War loves to capture and eat small-size fish, plankton, worms, and crustaceans. Equipped with a healthy appetite, they are known to eat as many as 120 larval fish in one day! The dactylozooid tentacles sport cells called nematocysts, which, when they penetrate prey, release venom that paralyzes the soon-to-be food for the Portuguese Man O’War. 

Don’t be fooled by the stinging tentacles though – the Portuguese Man O’War has many predators itself. These include the Loggerhead Turtle, Ocean Sunfish, Young Man O’War Fish, Blanket Octopus, Blue Dragon Sea Slug, Violet Sea Snail, and crabs. Each of these predators has a specifically curated strategy for avoiding the threat of stinging tentacles so that it can capture the Portuguese Man O’War as its own prey. For example, the Loggerhead Turtle’s skin is too thick for the nematocysts to puncture, and the young Man O’War fish takes advantage of their agile abilities to quickly dart in between tentacles while grabbing bites to eat from the non-stinging gastrozooids and gonozooids. The Blue Dragon Sea Slug takes their own approach to the matter – it consumes and integrates the stinging cells from the nematocysts into its own body as a defense mechanism. 

Going With The Flow

The Portuguese Man O’War is an invertebrate, which means it doesn’t have vertebrae, or a skeleton. Its tentacles can reach a length of 165 feet, and have an average span of 30 feet. Because it lacks any means of propulsion, the pneumatophore floats with the current about 6 inches above water, with tentacles submerged below. If threatened, the Portuguese Man O’War may temporarily deflate the pneumatophore and fully submerge until the coast is clear. 

“Portuguese man o’ war” by Joi is licensed under CC BY 2.0.

The lifespan of the Portuguese Man O’War is approximately 1 year. However, even when dying or amputated, the tentacles can still deliver a significant sting. 

While they are often found on beaches individually, our floating friend is also known to travel in groups of more than 1,000 with their fellow Portuguese Man O’Wars. Reproduction occurs through a process called “broadcast spawning.” Essentially, female Portuguese Man O’Wars release their eggs simultaneously with nearby males releasing sperm, and it all gets sorted out from there. Each pneumatophore leans to either the right or the left, dictating the path that the creature and its offspring take. This enables the species to grow across a greater geographic region. 

Ecological Obstacles

Not everything is always hunky-dory for this ocean faring creature. As ocean temperatures begin to rise on average due to global warming, the Portuguese Man O’War population has also begun to rise in number. This causes stress to the populations of its prey, which then decrease due to the greater demand. Furthermore, waterlogged plastic bags floating in the ocean resemble the Portuguese Man O’War – a food source – to sea turtles. 

Luckily, planet-cooling efforts are well underway here at Bio4Climate and beyond to ensure that ecosystems maintain balance, even through the increasing climate emergency. Words like “heat” and “temperature rise” have populated the news lately as global warming makes its presence known, and we have the solutions to mitigate these issues. Click here to learn more about what cooling entails and how you can get involved: https://bio4climate.org/era/practice/

“Sea” you soon,