Portuguese Man-o-War

The un-natural bloom of "Physala physalis" better known as the Portuguese Man-o-War that Gibraltar has been seeing this past week or so; can be put down to the last two months of South Westerly storms we have been having.

These winds have brought this species to our shoreline with waters from the Atlantic.

Physala physalis is a Siphonophore that uses a gas filled float to stay on the surface; the same float provides its movement through the surface waters in the direction of the prevailing winds. Other parts of the colony (it is a colony of animals all working to the same end) make up the digestive track and tentacles for capturing their prey.

The tentacles carry a powerful sting, stretching down and behind as the wind moves them forward, they should be given a very wide berth by swimmers and divers alike. They have been known to cause heart-attacks to some who have come into contact with the tentacles, which can be several metres long.  Where there is one there will be others, and it must be remembered when they are washed up on the shore line or beach the tentacles can still deliver their powerful sting.

Their main predators are the loggerhead turtle (Caretta carretta) and a small opithobranch Glaucus atlanticus  - a  sea snail minus shell, also called a nudibranch.

Notwithstanding all the above, it’s quite beautiful to look at. Do note however, that the bright colours are your first and only warning when encountered; be that shore line habitat, beach or in the sea. A wide berth is the watch word and don’t touch!

Photographs in this article were provided by R. Senior