The
Siphonophorae or
Siphonophora, the
siphonophores, are an
order of the
Hydrozoa, a class of marine
animals belonging to the phylum
Cnidaria. Although a siphonophore appears to be a single
organism, each specimen is actually a
colony composed of many individual animals. Most colonies are long, thin, transparent
pelagic floaters. Some siphonophores superficially resemble
jellyfish, one example being the
Portuguese man o' war (
Physalia physalis).