The Atlantic Portuguese Man-o’-War … Delaware Nature 101

The Atlantic Portuguese Man-o’-War

The Atlantic Portuguese man-o’-war (physalia physalia) has recently been spotted washed up on a Delaware beach. Normally, these animals are found in warm, tropical to subtropical waters. So how did this one end up on a Delaware beach? We will take a closer look at how this venomous marine animal found its way to Delaware. These amazing creatures should stir more fascination than fear but let’s take a look at what makes the Atlantic Portuguese Man-o’-War complicated, yet dangerous.

Portuguese man o war, delaware, sussex county
Man O War floating on the sea, the tentacles can be seen behind it and there are small white dots in the water around it are salps … photo by Cindy Fry

The anatomy of the man-o’-war is complex. This is not one living thing, but a symbiotic relationship, a working colony, of multiple living organisms. The man-o’-war is not a jellyfish, although it is a distant cousin. It is a siphonophore. There are four main parts or polyps.

  1. Pneumatophore (The bag that floats on top)
  2. Gastrozooid (The digestion system)
  3. Dactylzooid (The defense/prey-catching system)
  4. Gonozooid (The reproductive system)

Let’s start at the top. The gas-filled bag that floats on top of the water is the pneumatophore (new-mat-oh-fore). The pneumatophore is filled with gases including carbon monoxide (CO), oxygen (O), and argon (Ar). This polyp is what gives the man-o’-war the ability to use tides, winds and currents to travel. There is no propulsion device, such as fins, and they travel only by tides, current and winds. However, they can ‘lean’ one way or another to help direct travel. This is mostly for breeding purposes.

The man-o’-war congregate up to hundreds or thousands at a time for spawning. So how did this one end up on a Delaware beach? The answer is currents, wind and the gulf stream. Southern winds, currents and the golf stream pushed the man-o’-war north up the coast. This could be results from storms and other dramatic weather patterns too. Delaware occurrences of man-o’-war aren’t common place, but we do see them each year.

fenwick island, man owar, delaware, sussex county
Man O War on Fenwick Island this morning. Look at all the colors.
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The other three parts, or polyps, of the man-o’-war are zooids, including the gastrozooid for digesting prey, the dactylzooid for defense and catching prey, and the gonozooid for reproduction. The man-o’-war preys on fish, fish larvae, squid, and other cephalopods. Because the AP can’t propel themselves, they catch prey by stretching out and dragging their extremely long tentacles, up to 150 feet, in the water. The tentacles are covered in thousands of nematocysts (microscopic coiled hooks) that inject venom. When passing prey touch the tentacle, the nematocysts spring into action injecting venom into the prey causing paralysis and death. The tentacles contract and bring the fish up to the gastrozooid for digestion. The AP does have predators including the sand crab, loggerhead sea turtles and the sunfish (mola mola).

Man O War in Delaware, sussex county, delaware seashore state park,conquest, tower road
Man O War strewn in a line with the float popped.

So what do we do if we come across one? Don’t panic. The last thing you want to do is panic and become caught up in the tentacles. What if it is washed up on the beach, like this one was? Do not touch it and keep your distance. Tentacles can inject venom in or out of water and for hours or even days if severed from the rest of the man-o-war. Remember, the tentacles are an entirely separate organism so it will continue to function for a little while. Ocean swimmers can come into contact with severed tentacles and come out of the water with large, red welts, complaining of burning and stinging.

The venom is a neurotoxin intended to paralyze victims. Humans are not on the menu but contact does happen. If it does, it is important that you do not rinse it with water. This can further spread any remaining nematocysts on to more of the body causing further injury. The University of Hawaii recommends you rinse with white vinegar and apply heat. This method will remove any clinging nematocysts and deactivate the venom. Seeking medical attention is advisable because some people can have a severe allergic reaction that could be fatal. Fatalities are rare and are a result of anaphylactic shock.

The Atlantic Portuguese man-o’-war is an interesting species that needs to be observed from afar. While sightings are rare, please spread the word so we can keep other beach-goers safe. The man-o’-war is an important species in our ocean ecosystem and is another reason why Delaware waters are so unique and beautiful.

Did you enjoy learning about the man-o’-war? Learn about more species like this at Delaware Nature 101 Facebook Page.

Kara Okonewski
Delaware Nature 101

Kara Okonewski … Delaware Nature 101

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