hydrozoan

This type of hydrozoan is called a siphonophore.

This marine hydrozoan is a small medusa which is common in warmer waters.

The most widely-known freshwater hydrozoan is Hydra, which is found in slow-moving waters.

A type of freshwater hydrozoan, Craspedacusta sowerbyi, can also be found in the pond.

Obelia longissima is a colonial species of hydrozoan in the order Leptomedusae.

Heterastridium is a genus of fossil marine Hydrozoan from the Upper Triassic.

Historically interpreted as a sponge or hydrozoan, recent studies are converging to its classification in the coralline stem group, placing it among the red algae.

They also feed on the dangerous jellyfish-like hydrozoan, the Portuguese man o' war (Physalia physalis).

Like all fire corals the net fire coral is a hydrozoan, consisting of a colony of polyps with a calcareous skeleton.

Scenella tenuistriata is an extinct species generally classified as a mollusc or hydrozoan in the family Scenellidae.

Crystal Jelly (Aequorea victoria) of the Aequoreidae, a bioluminescent hydrozoan.

For the hydrozoan animal genus, see Stauridium (hydrozoan).

Since it is classified as a hydrozoan, it is one of many jellyfish that are also known as hydromedusae ("medusa" is another word for jellyfish).

Turritopsis nutricula, the immortal jellyfish, is a hydrozoan whose medusa, or jellyfish, form can revert to the polyp stage after becoming sexually mature.

In one species, Hydrichthys sarcotretis, parasitism is taken a stage further when the hydrozoan attaches itself to the copepod Cardiodectes medusaeus.

Gonionemus is a genus of hydrozoan that uses adhesive discs near the middle of each tentacle to attach to eelgrass, sea lettuce or various types of algae instead of swimming.

Physalia utriculus, also called Blue Bottle or (Indo-Pacific) Portuguese Man-of-War, is a marine hydrozoan of the order Siphonophora found in the Indian and Pacific oceans.

Well-known members of the Conica are the "air fern" (Sertilaria argentea) of the Sertulariidae which is sold dried as novelty "plants" and aquarium ornaments, and the Crystal Jelly (Aequorea victoria) of the Aequoreidae, a bioluminescent hydrozoan.