The sailing danger

This post is also available in: Dutch, Papiamentu.

Portuguese man-of-war in extended glory

Every year, during the period in between Carnival and Easter, popularly known as Lent (temp’i kuaresma), the wind pattern in our region tends to be irregular. When the directions from which the winds originate shift towards the south-east, our island might receive visits from a bizarre organism, one that we often are not too happy with. This organism belongs to the order siphonophora, and this word stands for animals ‘with hollow tubes’. We are talking about the Physalia physalis, commonly known as the Portuguese man-of-war (Pèchi Portugés in papiamentu).

Although it seems weird, the Portuguese man-of-war is not a single animal. Biologically speaking, it is a colony of organisms called hydroids, which are organized in such a way that they all have assumed a specific task. For example, groups of cells deal with digestion of food, other cell groups take care of reproduction, another cell acts as the pink-purple, gas-filled, float (the “hollow tube”), and then there are the so-called nematocysts, the dreaded stinging cells arranged in long tentacles hanging below the floating bladder. These tentacles are retractable, but while stretched out below a sizable colony, they can reach lengths of 30 meters. And that makes the man-of-war dangerous to swimmers, of course. The colony uses the stinging cells for defense and paralyzing prey. Yet there is one species that has adapted in such way that it has become impervious to the poison. The banded man-of-war fish, Nomeus gronovii, live among the tentacles of the Portuguese man-of-war and feed on scraps from the prey captured by the colony.

Sketch of a nematocyst, showing the thread and the trigger hook

The float allows the colony to be propelled by the wind, and that’s the reason that during southerly winds we might encounter groups of colonies along the south coast of our islands, along exactly those coastlines where all the swimming beaches are located. We might occasionally encounter Portuguese man-of-war along the north coast lines year around. It is not that they just occur during Lent in our neighborhood.

A nematocyst, the dreaded stinging cell, consists of a microscopically small bag filled with a rolled up thread terminating in a needle with barbs. This cell is pressurized. If a prey animal or a swimmer touches the trigger-hook of the cell, it will burst open, and the needle with attached thread will be shot in the direction of the victim with considerable speed. On contact a potent poison is injected into the victim. Touching the tentacles of a Portuguese man-of-war will trigger tens to hundreds of cells, causing intense pain and considerable blistering.

Stranded man-of-war, immobilized but still dangerous

Despite the bad reputation of these bizarre, but also very special colony-forming hydroids, their floating lifestyle is a benefit to beach guests. They are clearly visible. The advice is simple: if you observe a pink-purple balloon floating on the water, make sure to get out of the water right away. Better safe than sorry! If you do come into contact with the stinging cells, then a trip to a first aid clinic is recommended, especially in severe cases. By the way, never touch a stranded man-of-war, especially keep away from the stringy mass. The stinging cells may remain active for days, although the colony itself looks completely dead and dried out.

Leon Pors

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