(Physalia physalis), a relative of the jellyfish that floats on the surface (neustonic) in warm oceans. They are blue in colour with a large gas-filled float beneath which hangs the main body, and are often found lined up in windrows and slicks. The body consists of polyps, modified as feeding tentacles, or for digesting prey, or for reproduction. The tentacles are enormously extensible and a 30-centimetre (12-in.) float may be trailing 30 metres (100 ft) of tentacles, which are armed with powerful stinging cells (nematocysts). These discharge in response to touch and chemical stimuli, killing their prey of small fish and plankton. They can also sting humans painfully and can cause anaphylactic shock that may temporarily paralyse a swimmer. The tentacles are blue and difficult to see in the water, and can still sting even after becoming detached from the colony. The float is set on the body so that some animals tack to the right and others to the left. In the sea individual Portuguese men-of-war are often accompanied by one or more man-of-war fish (Nomeus gronovii). This has blue and silver vertical stripes, swims with immunity amongst the animal's tentacles, and lives in symbiosis with it, gaining protection, and possibly some food, from its host. The Portuguese man-of-war is not without its predators; loggerhead turtles (Caretta caretta) eat them regularly.
M. V. Angel
Subjects: Maritime History.