Calycophorans- Siphonophores with a nectosome and siphosome, but no pneumatophore.
Cnidaria- A group of animals that includes siphonophores, corals, sea anemones, Hydra, true jellyfish, hydroids.
Cormidium- A single iteration of the repeating pattern of zooids in the siphosome.
Cystonects- Siphonophores with a pneumatophore and siphosome.
Eudoxid- The released, free-living mature cormidia of calycophorans.
Nectophore- A medusa specialized for swimming. Sometimes called a swimming bell.
Nectosome- The region of a siphonophore colony that contains the nectophores. It is just below the pneumatophore (if present), and just above the siphosome.
Physonects- Siphonophores with a pneumatophore, nectosome, and siphosome. Two physonect genera, Athorybia and Melophysa lack a nectosome, but have other features that clearly unite them with this group and the development of these animals shows that the nectosome has secondarily been lost.
Pneumatophore- A carbon monoxide filled float found in cystonects and physonects.
Siphosome- The region of a siphonophore colony that contains the feeding, reproductive, and defensive zooids. The zooids of the siphosome are arranged in a species specific, repeating linear pattern.
TENTILLUM (tentilla, plural)- The side branch of a siphonophore tentacle. Each tentacle can have tens to hundreds of tentilla. These structures contain most of the nematocysts (stinging capsules) of the colony, and are what actually capture the prey. The tentilla of some species are passive, stinging prey items that happen to touch them. In other species, the tentilla act as lures.
Zooid- The units that make up a colonial animal. Each zooid is structurally similar to a free living animal, but in a colonial animal they are all joined together and share nutrients as well as information about their environment.