Animal profile

Hydra

Hydra vulgaris

HydrozoaStill and slow-moving fresh water, attached to plants and debris

Field profile

Hydra is a small freshwater hydrozoan a few millimetres long, with a tubular body, an adhesive basal disc and a ring of tentacles. It has no medusa stage. It is a long-standing laboratory model for regeneration and stem cell biology.

Published field notes

2026-03-18

Hydra

A hydra can rebuild itself from a fragment

Cut a hydra into pieces and each sufficiently large piece regrows a complete animal, head and foot correctly placed. Even dissociated cells, reduced to a suspension and left to reaggregate, can reorganise into a functioning hydra.

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