Hydra look much like a very small long thin sea anemone but are only found in freshwater. In the same way as marine sea anemones, they have long stinging tentacles for catching prey such as small insects or crustaceans and hold onto plants and rocks with the base of their body. They move by cart-wheeling with their tentacles or by repetitively somersaulting from tentacles to base and back again. In order to reproduce they usually asexually grow a bud off of their main truck which then falls off and develops into a smaller Hydra. They may also reproduce sexually by passing sperm and eggs between either themselves or another hermaphroditic Hydra. The green colour in Hydra is from a green algae called Chlorella vulgaris which lives in the Hydra's stomach. The relationship between the two kinds of organisms is thought to be beneficial to both organisms, with the algae utilising the carbon dioxide produced by the Hydra's. The food and oxygen requirements of the Hydra may also be met to some extent by the production of carbohydrate and oxygen by the algal cells during photosynthesis.
Conservation status: Hydra are widespread, require reasonable water quality and may be extremely common when food is abundant.
Conservation status: Freshwater jellyfish are not native to New Zealand and are well spread through out the world in good numbers. 