Hydra viridissima

Taxobox
name = "Hydra viridissima"

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image_width = 250px
image_caption =
regnum = Animalia
phylum = Cnidaria
classis = Hydrozoa
ordo = Hydroida
familia = Hydridae
genus = "Hydra"
species = "H. viridissima"
binomial = "Hydra viridissima"
binomial_authority = Pallas, 1766

"Hydra viridissima" also known as the green hydra, is a cosmopolitan species of hydra found in both temperate and tropical fresh waters. The characteristic green colour comes from cells of the unicellular alga Chlorella within the cells of the gastrodermis.

When disturbed, Hydra retracts to a small green blob which is easily overlooked. Gently sweeping through a clean weedy pond and allowing the collected water and plant matter to stand in a jar will often reveal a Hydra re-emerging after only a few minutes.