Hydrozoa are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most living in saltwater. The colonies of the colonial species can be large, and in some cases the specialized individual animals cannot survive outside the colony. 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, the freshwater polyps, Obelia, the Portuguese Man o' War, the chondrophores, "air fern", and the pink-hearted hydroids. Wikipedia [ - ]

Hydrozoa are a taxonomic class of individually very small, predatory animals, some solitary and... [ + ]