Portuguese Man o’ War roam worlds oceans. They are most abundant in (sub)tropical waters, but can be found in colder seas too. About their way of life and distribution not much is known. The following blog treats their occurrence on shores were you wouldn’d expected them.
The common name of these animals comes from a Portuguese war ship type of the 15th and 16th century, the man-of-war or caravel (in Portuguese, Caravela), which had triangular sails similar in outline to the float of sail of the Portuguese Man o’ War.
Physalia species (scientific name of the Portuguese Man o’ War), look like jellyfish but are in fact siphonophores; not a single organism but a colony of highly specialized individuals. These zooids are specialized for digestion, reproduction or to form a float or sail. The Portuguese Man o’ War secretes gas into the float (this gas has the same composition as air, but can maintain high levels of carbon dioxide); this allows them to sail the surface of the ocean. They are able to deflate the sail and submerge in case of attack of a predator. Although Portuguese Man o’ War are not of commercial value, they are well studied because of their venomous sting. Their sail may reach 9 to 30 centimeters, but their tentacles, which dangle from their body, may reach a length of 22 meters (66ft) and are covered with numerous venom-filled nematocysts. Their sting is dangerous or even lethal to man, and always very painful. Even stranded, the venom stays active, so take care!
There is still much unknown about the distribution and systematics of the Physalia group. Bruce Halstead, an authority on venomous marine creatures, states two species: Physalia physalis Linnaeus, 1758 (the “classic” Portuguese Man o’ War) and Physalia utriculus La Martinière, 1787 (the Bluebottle). The first is found tropical Atlantic waters, while P. utriculus occurs in the Pacific and Indian Oceans. I found both species during some of my travels. In New Zealand, South Island – 1995 – my dear friend Saskia Wood and I visited the Mahinapua coastline and found the high watermark covered with Bluebottles. When visiting South Africa in 2009 Hans Post and I witnessed an invasion of Bluebottles on the Beaches of Nature’s Valley and Keurboom’s Lagoon. Those sightings match the known distribution of Physalia utriculus.
More puzzling is the observation I did with Erwin Kompanje on the beach of Praia da Marinha, Algarve, South Portugal around Christmas 2009. When Erwin, his wife Ditty, and son Otto and I arrived at the beach, the weather was very bad, with a stormy Westerly wind and rain showers; but everywhere we saw the small bleu bubbles I recognized as Bluebottles. They were small (< 10 cm) and their float had the form of a Bluebottle and not at all like the classis Man o’ War that has a real sail on its float (see photo’s). But Portugal lies far North of the tropical part of the Atlantic Ocean (the known habitat of Physalia physalis) and maybe 10.000 kilometers from the regular distribution of Physalia utriculus.
What did we see? Real Bluebottles, young Portuguese Man o’ War, or another unknown species of Physalia? To me is clear more study is required on the enigmatic sea creatures.
 Halstead, B.W., Poisonous and Venomous Marine Animals of the World, 1988, Darwin Press