Hydrozoa (hydrozoans; from Ancient Greek ὕδωρ (húdōr) 'water' and ζῷον (zôion) 'animal') is a taxonomic class of individually very small, predatory animals...

Schuchert P, ed. (2012). "Turritopsis dorhnii (Weissmann, 1883)". World Hydrozoa database. World Register of Marine Species. Retrieved November 29, 2012...

individual is actually a colony of hydrozoan polyps. The taxonomic class, Hydrozoa, falls under the phylum Cnidaria, which includes anemones, corals, and...

Cnidaria, and is often considered a subphylum. It includes the classes Hydrozoa, Scyphozoa, Staurozoa and Cubozoa, and possibly the parasitic Polypodiozoa...

Siphonophorae (from Greek siphōn 'tube' + pherein 'to bear') is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria. According...

sea pens); swimming Scyphozoa (jellyfish); Cubozoa (box jellies); and Hydrozoa (a diverse group that includes all the freshwater cnidarians as well as...

Velella is a monospecific genus of hydrozoa in the Porpitidae family. Its only known species is Velella velella, a cosmopolitan (widely distributed) free-floating...

related more closely to scyphozoan jellyfish than either are to the Hydrozoa. Hydrozoa medusae also have tetra-radial symmetry, nearly always have a velum...

redescription of the Portuguese man-of-war, Physalia physalis (Cnidaria, Hydrozoa, Siphonophorae, Cystonectae) from Brazil". Iheringia. Série Zoologia. 97...

produce both testes and ovaries at the same time. Many members of the Hydrozoa go through a body change from a polyp to an adult form called a medusa...