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Blue Button, Porpita porpita
Scientific classification

Porpema; Porpita; Velella

The chondrophores or porpitids are a small and unusual group of hydrozoans. They are the family Porpitidae.[1]

They all live at the surface of the open ocean, and are colonies of carnivorous, free-floating hydroids. Their life-style in the plankton is similar to that of pelagic jellyfish.

The chondrophores look like a single organism but are cooperatives of polyps.

The most familiar members of the family Porpitidae are the Blue Button (Porpita porpita) and the By-the-wind Sailor (Velella velella).


Chondrophores may look like a jellyfish, but they really are not. Like the siphonophores they are not a single animal. They are a colony of clones, genetically identical zooids. These zooids are small, highly modified individual polyps. Though structurally similar to other cnidarians, the zooids do not live by themselves: they are attached to each other. Each type of zooid depends for survival on the others doing what it cannot do by itself.

This kind of set-up is also found in the siphonophores: the Portuguese Man o' War. They evolved independently, and are classified in different orders.

Fossil record

A rare soft-bodied fossil was got from Mississippian strata in northeastern Kentucky. It was interpreted as a chondrophorine float.[2] The origin of the group was probably in the Neoproterozoic era, some 650–540 million years ago.


  1. Schuchert, Peter 2012. The hydrozoa directory. Muséum Geneve. [1]
  2. Yochelson, Ellis L. and Mason, Charles E. 1986. A chondrophorine coelenterate from the Borden Formation (Lower Mississippian) of Kentucky, Journal of Paleontology. 60, 5, 1025-1028. [2]