Hydrozoa

Hydrozoa Temporal range: 575–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Siphonophorae
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Cnidaria
Subphylum:	Medusozoa
Class:	Hydrozoa Owen, 1843
Subclasses and orders[1]
Hydroidolina Anthoathecata Leptothecata Siphonophorae Trachylinae Actinulida Limnomedusae Narcomedusae Trachymedusae

Hydrozoa (hydrozoans; from Ancient Greek ὕδωρ (húdōr; "water") and ζώα (zóa; "animals")) is a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. 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 habitats. Hydrozoans are related to jellyfish and corals, which also belong to the phylum Cnidaria.

Some examples of hydrozoans are the freshwater jelly (Craspedacusta sowerbyi), freshwater polyps (Hydra), Obelia, Portuguese man o' war (Physalia physalis), chondrophores (Porpitidae), and pink-hearted hydroids (Tubularia).