Children (54 direct children, 54 direct and indirect children):
Hydra oligactis
Brown hydra
Hydra viridissima
Hydra baikalensis
Hydra ethiopiae
Hydra daqingensis
Hydra zeylandica
Hydra hadleyi
Hydra canadensis
Hydra mohensis
Hydra oregona
Hydra liriosoma
Hydra beijingensis
Hydra paludicola
Hydra iheringi
Hydra robusta
Hydra thomseni
Hydra japonica
Hydra umfula
Hydra paranensis
Hydra circumcincta
Hydra intermedia
Hydra minima
Hydra oxycnida
Hydra salmacidis
Hydra cauliculata
Hydra utahensis
Hydra rutgersensis
Hydra sinensis
Hydra plagiodesmica
Hydra viridis
Hydra harbinensis
Hydra vulgaris
Fresh-water polyp
Hydra javanica
Hydra intaba
Hydra madagascariensis
Hydra parva
Hydra mariana
Hydra hymanae
Hydra magellanica
Hydra americana
Hydra polymorpha
Hydra fusca
Hydra attenuata
Hydra shenzhensis
Hydra zhujiangensis
Chlorohydra
Pelmatohydra
Hydra braueri
Hydra brunnea
Hydra hexactinella
Hydra orientalis
Hydra rubra
Hydra tenuis
Hydra verrucosa