Balloon in water…wait what??


Portugese Man-of-war. Photo by Laurence Madin, Woods Hole Oceanographic Inst.


The Portuguese Man-of-War (Physalia physalis) is commonly mistaken to be a jellyfish due to its jelly-like outer appearance and tentacles, but does not belong to that family. It is instead, a colony of organisms called polyps (or zooids) which work together (King).

The Portuguese Man-of-War is often found floating on the surface of oceans, in warm tropical and subtropical parts of the world. It has no means of moving around, and instead relies on waves and currents to move around. This complete dependence on currents renders them vulnerable with no means of protecting themselves. As such, it produces venom which are released by its tentacles so as to protect itself from predators, as well as to enable it to feed.

As the man-of-war drifts around, it is constantly “fishing” for food with its tentacles that can hang in the water till 50 metres (King). Particularly fond of small fishes, crustaceans and planktons, the man-of-war’s venom paralyses them so as to prevent them from escaping their grasp. This is achieved with the aid of stinging capsules called nematocysts that cover most of the surface area of the tentacles. Nematocysts are “tiny, coiled, stinging barbs” that shoot out whenever the cells are disturbed by organisms brushing up against them, or by osmotic water changes.

The Portuguese Man-of-War is a good example of how beauty can be deadly (or harmful, rather). Its clear blue jelly-like float makes it seem delicate and vulnerable, but the tentacles beneath the surface of water certainly pack a punch.


i. “Portugese Man-of-war” by Laurence Madin, Woods Hole Oceanographic Institute. Retrieved from (Accessed 7 April 2013)

ii. King, R. (n.d.). “The portuguese man”. South Carolina Department of Natural Resources, Retrieved from (Accessed 7 April 2013)

iii. Portuguese man o’war – animal facts and information. (n.d.). Retrieved from (Accessed 7 April 2013)

iv. Hoover, M. (n.d.). Portugese man-of-war (physalia physalis). Retrieved from (Accessed 7 April 2013)