- Norwegian: kolonimaneter
The siphonophores are free-swimming or floating (pelagic) colonies. Unlike species of the two other major orders of Hydrozoans, the Athecate and Thecate hydroids, the medusae are never released from the stem. Sometimes the colony resemble a single animal, like the Portuguese Man o'War (Physalia physalis).
The colony is often held together by a long thread where different kinds of specialized animals are attached. Some digest food, while others are use stinging tentacles to catch their prey. They hand the food over to the "stomachs" that swallow and digest the food, and thus provide nutrition for the entire colony. Some even emit light.
The highly specialized colonies made the scientists regard the siphonophores as a very distinct group. In recent years it has been found that the siphonophores have evolved from simpler hydrozoans, similar to the hydroids. Consequently they are united with the hydroids in the subclass Hydroidolina of the class Hydrozoa. There are three suborders of siphonophores, Calycophorae, Cystonectae and Physonectae.