What is "physalia"

Physalia \Phy*sa"li*a\, n. [NL., fr. Gr. ? a bladder, fr. ? a bellows.] (Zo["o]l.) A genus of large oceanic Siphonophora which includes the Portuguese man-of-war.

Note: It has a large air sac, or float, with a sail-like crest on its upper side. Numerous zooids of different kinds are attached to the under side of the float. Some of the zooids have very long tentacles; some have a mouth and digest food; others produce gonophores. The American species ( Physalia arethusa) is brilliantly colored, the float being pink or purple, and bright blue; the zooids blue. It is noted for its virulent stinging powers, as well as for its beautiful colors, graceful motions, and its ability to sail to windward.

Physalia is a genus of the order Siphonophorae, colonies of four specialized polyps and medusoids that drift on the surface of the Atlantic, Indian and Pacific oceans. Although these organisms look like a single multicellular organism, each specimen is actually a colony of minute organisms called zooids that have to work together for survival. A gas-filled bladder resembling a blue bottle provides buoyancy, and long tentacles of venomous cnidocytes provide a means of capturing prey. A sail on the float, which may be left or right-handed, propels Physalia about the sea, often in groups. Individuals sometimes become stranded on beaches, where their toxic nematocysts can remain potent for weeks or months in moist conditions. Both species of this siphonophore resemble a jellyfish in appearance, with their bell and tentacles.

The species Physalia utriculus is given the common name Pacific man o' war to distinguish it from the more widely distributed and larger Physalia physalis, the Portuguese man o' war. The species are told apart by the size of the float (six inches compared to twelve) and by having a single versus several long fishing tentacles. No fatalities from envenomation are recorded for P. utriculus, in contrast to the larger species.

The genus was first described by Jean-Baptiste Lamarck in 1801.