Hydrozoa (hydrozoans) are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria.
Some examples of hydrozoans are the Freshwater Jelly (Craspedacusta sowerbyi), the freshwater polyps (Hydra), Obelia, the Portuguese Man o' War (Physalia physalis), the c...
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Hydrozoa (hydrozoans) are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria.
Some examples of hydrozoans are the Freshwater Jelly (Craspedacusta sowerbyi), the freshwater polyps (Hydra), Obelia, the Portuguese Man o' War (Physalia physalis), the chondrophores (Porpitidae), "air fern" (Sertularia argenta) and the pink-hearted hydroids (Tubularia).
Most hydrozoan species include both a polypoid and a medusoid stage in their life cycle, although there are a number that have only one or the other. For example, Hydra has no medusoid stage, while Liriope lacks the hydroid stage.
The hydroid form is usually colonial, with multiple polyps connected together by tubelike hydrocauli. The hollow cavity in the middle of the polyp extends into the associated hydrocaulus, so that all the individuals...
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