Siphonophora

Siphonophora is an order of the Hydrozoa, a class of marine invertebrates belonging to the phylum Cnidaria. They are colonial, the colonies can superficially resemble jellyfish and they may be Earth's most abundant predators. The best known species is the Portuguese Man o' War. Each Man o' War is a colony.

Siphonophora are especially scientifically interesting because they are composed of medusoid and polypoid zooids that are morphologically and functionally specialized. Each zooid is an individual, but their integration with each other is so strong that the colony attains the character of one large individual; and most of the zooids are so specialized that they lack the ability to survive on their own. Thus siphonophora exist at the boundary between colonial and complex multicellular organisms. Also, because multicellular organisms have cells which, like zooids, are specialized and interdependent, siphonophora may provide clues regarding their evolution.

Erenna genus
A siphonophore from the genus Erenna has been discovered at a depth of around 1,600 meters off the coast of Monterey, California. The individuals from these colonies are strung together like a feather boa. They prey on small animals using stinging cells. Among the stinging cells are stalks with red glowing ends. The tips twitch back and forth creating a twinkling effect. It is theorized that twinkling red light attracts small fish that have been found eaten by these siphonophores.

While many sea animals produce blue and green bioluminescence, this siphonophore is only the second found to produce a red light (the first being the scaleless dragonfish).

Haeckel's siphonophores
Ernst Haeckel described a number of siphonophores, and several plates from his Kunstformen der Natur (1904) depict members of the taxon.