Siphonophore << sy FAHN uh fawr >> is among the strangest creatures found in the oceans. A siphonophore is not a single living thing. Rather, it is a colony of individual organisms, called zooids << ZOH oydz >>, arranged in a long string. All of the zooids descend from a single initial zooid. Within the colony, each zooid serves a specialized function, such as movement, digestion, or reproduction. The body of the colony is jellylike and fragile, and individual zooids may easily become separated. However, a zooid cannot survive in separation from the colony. Siphonophores challenge traditional ideas about what it means to be an individual. Each zooid is a distinct organism, a clone of the original zooid. However, the entire colony functions much like a single living thing.
Siphonophores are cnidarians, a group of animals that also includes jellyfish and corals. There are many different species of siphonophore. The most well-known siphonophore is the Portuguese man-o-war, sometimes mistaken for a jellyfish. Most siphonophores live in the open ocean. Some live at great depths. Some species can reach great lengths. A huge siphonophore discovered off Western Australia measured an estimated 150 feet (45 meters) long. It was floating in a loose coil some 2,000 feet (600 meters) below the surface. Many species of siphonophore are able to produce their own light, an ability called bioluminescence. 
Siphonophores feed on crustaceans (shellfish), tiny fish, and other small animals. They capture their prey by trailing long tentacles. The tentacles contain stinging capsules called nematocysts. The nematocysts harpoon prey and inject a toxin, immobilizing it. Many siphonophores simply wait for prey to swim into their tentacles. At least one deep sea species has been found to lure its prey with light.
Siphonophores reproduce sexually through the use of specialized zooids. In some species, the entire colony functions as either male or female. Colonies of other species have both male and female parts. A new siphonophore begins with a single zooid formed from a fertilized egg. This zooid produces the rest of the colony through budding. Budding is a form of asexual reproduction in which a new organism grows from a bud on the original organism.
