Wednesday, August 29, 2018

Pacific Portuguese Man-of-War

Aloha everyone!

On a three-day-program with students from Beijing this past month, much of the Community Education Program team was snorkeling on the sand bar, when I had to bring one cold student back to our boat. On my way back to the other snorkelers, I got caught in the long tentacle of a Pacific Portuguese Man-of-War (Physalia utriculus /pa'imalau)!

A Pacific Portuguese Man-of-War swimming in Hawaiian waters.
Its float and some of its medusae are visible,
with the longer fishing tentacle drifting further below the picture.
Photo by
Pacific Portuguese Men-of-War, otherwise known as bluebottles, belong to the phylum Cnidaria, meaning that they have a stomach and mouth, radially symmetric curved bodies which open at one end, and tentacles covered in stingers or nematocysts. These nematocysts help cnidarians to be able to eat and protect themselves. A cnidarian can either be in the form of a polyp or a medusa, where the polyp is attached to a surface with its mouth pointing upwards (i.e. an anemone or a coral) and the medusa form faces down and is free-swimming (i.e. a jellyfish). A Man-of-War is in the medusa form of a cnidarian since it faces downwards as shown on the right.

Though many people refer to these gelatinous creatures as jellyfish, they actually belong to the class Hydrozoa, unlike true jellyfishes which are as scyphozoans and cubozoans. Hydrozoa create their medusae through budding, or asexual reproduction through the creation and cleavage of a clone on the hydrozoan. Syphozoa on the other hand, use strobillation, or the spontaneous segmentation of  their bodies to be able to create their medusae, while Cubozoa polyps metamorphose to become medusae.

The Pacific Portuguese Man-of-War belongs to the order Siphonophora within the class Hydrozoa. Typically, these open-water or pelagic animals use their floats (the puffy-looking polyp above the tentacles and medusae) in order to rise and sink in the water column. They can do this by altering the amount of gas or oil within their floats, or by swimming. Unlike other hydrozoans, the Man-of-War stays at the surface, using its carbon monoxide-filled float to keep it above the water, with a crest to help it move with the wind. Though cnidarians can be either solitary or colonial, and the Man-of-War may look like one solitary animal such as a jellyfish, they are actually made up of many medusae and polyps, which bud from the original polyp (the float) as mentioned above, and attach to it to form a colony. The medusae hanging below the float can also help with propulsion through the water, and each perform specialized tasks such as digestion, fishing, and sexual reproduction via eggs and sperm. A single tentacle extends down into the water column, paralyzing or killing its prey before contracting to feed itself. Check out how these animals move in the videos linked below:

An image of a Man-of-War's float with its
long tentacles trailing behind it.
Photo by Arina Habich.
A picture of me after I got stung. You may be able to
see the red mark from the right side of my mouth across 
my upper lip, and up to where I am pointing on my cheek.
The tentacle got caught around my snorkeling mask!
Photo by me.

Since these creatures are a dark blue or even purple color, they are difficult to spot in the water, until it is too late. Your best chance of seeing one before it stings you is by looking for its float above the surface of the water. If you do happen to get stung, however, recent research by UH suggests that vinegar works well at stopping cnidae discharge which causes the stinging. Other methods of stopping stinging such as alcohols, urine, shaving cream and baking soda actually caused cnidae discharge and did not stop it from happening. This means that these methods which were previously thought to be a better method for stopping Man-of-War stings do not seem to help at all, and may actually harm you more!

After being stung, the burning for me personally lasted about an hour until it was completely gone. However, I had been touching it before I knew not to do that, and instead to rinse with salt water and vinegar. Some people and sources seem to suggest that this feeling will only last for about 20 minutes, while others say that they had pain and red marks in those areas for about a week! I suppose that everyone's pain tolerance is different, and some people may have sensitive skin or allergies as well. For me, though, the pain just felt like a very bad razor burn.

An image showing the relative size of a Pacific Portuguese Man-of-War compared to a person's foot. That thin tentacle is what wrapped around my snorkeling goggles, stinging me across the face. Even though these creatures are fairly small compared to us, their sting sure packs a punch!
Photo by

Fortunately I got stung by the Pacific Portuguese Man-of-War, which can have a float of about 1 to 2 inches in length and a long tentacle below, instead of the Atlantic version which can have a float up to a foot long, with many fishing tentacles up to 30 feet long! Though I was the only person to get stung out of our snorkeling group, some of our other staff members noticed a cloud of Men-of-War floating towards the school group on their way back to the boat after I had been stung, since it was such a windy day. It looks like this intern took one for the team!

Mahalo nui,

Ginny Svec
Our group of students snorkeling with one of our CEP staff members, Kyla. A short distance away was where all of the Men-of-War were swimming.
Photo by Leon Weaver.

Bouillon, Jean, et al. An Introduction to Hydrozoa. Publications Scientifiques Du Muséum, 2006.

Hoover, John P. Hawai'i's Sea Creatures: a Guide to Hawai'i's Marine Invertebrates. Mutual Pub., 1999.

Wilcox, Christie L., et al. “Assessing the Efficacy of First-Aid Measures in Physalia Sp. Envenomation, Using Solution- and Blood Agarose-Based Models.” MDPI, Multidisciplinary Digital Publishing Institute, 26 Apr. 2017.

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