Hydranth and hydrotheca of Clytia hemisphaerica (Linnaeus, 1767) (Leptomedusae, Campanulariidae).

The hydranths (yellow arrow) of Clytia hemispaerica are protected by a hydrotheca (red arrow), a rigid, beaker-like skeletal structure. The presence of a hydrotheca is diagnostic for the polyps of the taxon Leptomeduse. The height of the hydrotheca is about 0.5 mm. Note also the undercut hypostome, a characteristic trait of the Proboscidoidea.