green Hydra with extended tentacles

Green Hydra ( Hydra viridis ) is a freshwater coelenterate that predates on small animals such as Daphnia or Cyclops. Although multicellular it is small ranging from .5 to 3 mm. It is a common organisms found in still waters from early spring to late autumn. The characteristic green colour comes from cells of the unicellular alga Chlorella within the cells of the gastrodermis. Because of this, they are generally less predacious than aposymbiotic hydra species.