A better look at the Portuguese man-of-war

By: Ashley Gustafson

Portuguese Man-of-war close up

Beautiful, ethereal, mesmerizing; Odds are one look at the Portuguese man-of-war will leave you wanting another. Best known for its painful sting, this infamous ocean dweller is not a popular beach guest. This vibrant but mysterious invertebrate is an excellent example of an organism appearing to be one animal but is actual a whole colony. The Portuguese man-of-war is assumed by many to be a jelly fish based on its gel like consistency and long tentacles, while in fact it is a colonial organism called a siphonophore. Siphonophores are closely related to jelly fish but the major difference is jelly fish are a single organism while siphonophores are made up of multiple organisms. In siphonophores, the colony of organism’s work together and each organism serves a purpose within the colony. They do this by having genetically identical, individual organisms responsible for different tasks instead of having specialized tissues or organ structures like a single organism would. Some examples of responsibilities of these separate organisms are feeding, locomotion, and reproduction. In the Portuguese man-of-war there are four separate organisms that work toget

her as one: the pneumatophore, the tentacles, the gastrozooids, and the reproductive organism.

As you can see from the picture above, the Portuguese man-of-war is beautiful shades of blue, purple, and violet. They are characterized by a large “sail” that looks like a glass-blown bubble that sits above the water and allows them to move as the wind blows. This “sail” is the pneumatophore or the gas-filled bladder. This is quite revolutionary for a siphonophore, as they are normally stationary and have to wait for their prey to come to them. By having this “sail” they are able to move via wind to catch their prey. This “sail” is also how they received their nautical themed name as it looks like an old war ship at full mass. The Portuguese man-of-war is a carnivore and eats pretty much anything small enough for it to catch in its tentacles like small shrimp, small copepods, and small fish. Its tentacles can be upwards of 165 feet long but on average are about 30 feet long. Once the Portuguese man-of-war captures its prey, muscles in its tentacles move the prey up to the digestive organism or the gastrozooids that “eat” the food and spread the nutrients to all the organisms in the colony. The Portuguese man-of-war is commonly found in large groups. It is not uncommon for a whole beach to close down based on the appearance of one single man-of-war since it is likely many more are in the area.

full body portuguese man of war

Is the Portuguese man-of-war a threat to me?

While the Portuguese man-of-war delivers a nasty sting, it is not lethal the majority of the time. There are many factors that come into consideration, and each sting should is assessed based on the sex of the person stung, the age, where they were stung, and how many times that person was stung. The long tentacles of the man-of-war allow it to catch prey as it floats along via pneumatophore through the open ocean. Unfortunately, these sails will sometimes take the man-of-war to beaches in sub-tropical waters throughout the Caribbean, Atlantic, Pacific and Indian oceans which also happen to be popular recreational destinations for locals and tourists which is why sometimes people get stung by them. There tentacles are covered with venom filled nematocysts or simply stinging cells. When these cells come in contact with prey or a threat, they inject a potent mixture of venom into the victim. This venom is a deadly cocktail of toxins to prey. It is made up of several compounds that all add to the man-of-war immobilizing and capturing its prey. One of these compounds creates holes in the prey’s cell membrane, causing its demise. Another compound of the venom will break down important proteins and fats that insulate and protect the prey’s cells allowing the Portuguese man-of-war to begin digesting its prey simply on contact. As previously stated, the venom of the Portuguese man-of-war is generally more painful than lethal in humans but factors do come into play. For example skin thickness can affect the effectiveness of the sting. In woman and children skin is thinner than in men so woman and children have more adverse reactions to the sting of a man-of-war then men do. Also being stung in a place of direct blood flow can be lethal to any. For example, if a woman gets stung in the neck, and the venom is injected directly into the bloodstream it has potential to be deadly. However, if a woman gets stung in the lower back, odds are it will be painful but only cause irritations similar to splinters being stuck in the skin. Another factor that also comes into consideration with the Portuguese man-of-war is numbers, as normally there is usually more than one of them since they often exist in groups. It is fairly intuitive and completely correct to assume that the more times a person is stung, the more venom is injected in them, and that means more potential for fatality. Thus it is common for community beaches to close when they are spotted, not based on the sting of the individual but the potential of a “swarming” affect and multiple stings from multiple man-of-wars which could be lethal. In summary, the Portuguese man-of-war is a creature to be wary of when visiting the beach but shouldn’t stop anyone from enjoying the beautiful waters they are found in.

Still a Mystery

While the Portuguese man-of-war causes great fascination based on its vibrant colors, large tentacles, and strange body plan, there is not very much known about them. Recently more work has been done to learn more about the man-of-war but they are a subject that possesses many difficulties for scientists and their arsenal of research methods. Their jelly consistency and open-ocean lifestyle make them difficult to study not only in a laboratory setting but also in a wild, natural setting. Their body composition makes it impossible with current technology to insert radio transmitters to track movements. They also do not do well in captivity. For unknown reasons, researchers have struggled to keep the Portuguese man-of-war in captivity for the entire range of their lifecycle and thus far have only been able to keep them through certain parts. For these reasons, researchers do not even have a definite life span for these organisms. While there have been many struggles researchers have learned some pretty interesting things about the man-of-war. First, it has been proposed that the blue, purple, and violet colors of the air-bladder “sail” protect it from UV radiation from the sun. This is important because this “sail” is above the water and constantly exposed to the sun and its radiation. UV radiation degrades the integrity of cells, causing cell mutation and furthermore causing cancer.

In recent events, the Portuguese man-of-war has come to the attention of many nature enthusiasts and photographers as its natural hypotonic looks are astounding not only in still film but moving film as well. Natural Geographic has led the way with its “Portrait of the Portuguese Man-of-war” last year. This absolutely incredible photography is breath-taking and looks at the man-of-war in a new light of admiration rather than fear. More and more people are finding the beauty in cnidarians like jelly fish and siphonophores like the Portuguese man-of-war. Their ethereal effect and fluid motions have a calming affect that is catching on within the masses. Hopefully this trend in art, photography, and film will inspire more interest and research for these fascinating siphonophores. Make sure to check out the video below in references to get an innovative look at the Portuguese man-of-war!