Green hydra

Hydra viridissima · The green hydra is a tiny freshwater cnidarian that lives in still or slow-moving water across the Northern temperate zone.

Green hydra
Photo: Patrick Hacker, CC BY 4.0
Green hydra
Photo: Patrick Hacker, CC BY 4.0
Green hydra
Photo: Patrick Hacker, CC BY 4.0

Taxonomy

KingdomAnimalia
PhylumCnidaria
ClassHydrozoa
OrderAnthoathecata
FamilyHydridae
GenusHydra
SpeciesHydra viridissima

Where it lives

Weedy ponds and lakes in temperate regions around the world.

Fun facts

  • The green hydra gets its color from tiny green algae that live inside its body.
  • Although hydras mostly stay put, they can travel by somersaulting: they detach their foot, then bend over and over to flip to a new spot.
  • A hydra can also float to the water surface upside down, carried by a gas bubble made on its foot.
  • After a long stretch of darkness makes the algae disappear, the algae can multiply and repopulate the green hydra in about two days once light returns.

Play it

The Green hydra was the creature in a regional daily on November 11, 2026. Can you identify tomorrow's from its photos? Every day brings a new creature to place from kingdom to genus, map and name.

Play today's creature or replay a past daily

Facts and taxonomy adapted from Wikipedia (CC BY-SA 4.0).