Trachymedusae

Trachymedusae belong to the phylum Cnidaria and the class Hydrozoa. The Trachymedusae include five families, among which are 30 genera and around 50 species in all. The family Rhopalonematidae has the greatest diversity.

==Description== Trachymedusae are identifiable by their umbrella edge which lacks any lobes. The tentacles at the edge of the umbrellas are solid or solid and hollow, there is a thickened tissue ring that has a large number of nematocysts, the radial canals number from four to six to eight and more than eight, though eight is the most common amount found. The sensory clubs can be open or closed with the endodermal axis. The gonads are generally located at the radial canal or where the radial canal and the manubrium connect. The cnidome may have stenoteles. Trachymedusae reproduce sexually during the medusa stage lacking a polyp stage.