Portuguese man-of-war tentacles
The Portuguese man-of-war, Physalia physalis (Siphonophorae - Physaliidae) stands out for its beauty, its deadly effectiveness, and its composition. This is not a jellyfish, but a siphonophore, which takes form and function through the aggregation and physiologic integration of numerous individual zooids, each small and specialized, scarcely capable of life on its own. It is the organization of zooids into polyps that enables the man-of-war to float, feed, reproduce, and sting.
The Portuguese man-of-war is found in the Pacific and Atlantic oceans and consists of a floating colony composed of several types of polypoid individuals attached to a free-floating stem. It has very long tentacles (as long as 30 m), has a large float containing nitrogen and carbon monoxide, and has up to 750 000 nematocysts on each of its 40 tentacles.
Envenomation by Portuguese man-of-war stings may cause fatalities due to respiratory failure and hypotension. Physalia physalis toxins cause hemolysis, mast cell degranulation, vasodilation, and conduction disturbances.
Photo credit: ©Alvaro Migotto | Locality: CEBIMar, University of São Paulo, Brazil (2006)