Hydra
Hydra spp. · Aquatic life
Whole animal · Photo: Patrick Hacker / CC BY
Also called Brown hydra, Freshwater hydra, Green hydra, Chlorohydra
How to identify Hydra
- Tiny tube shaped animal about 1/4 to 3/4 inch when stretched out
- Crown of 4 to 12 thin tentacles at one end
- Attached to plants, rocks or aquarium glass by a sticky foot
- Shrinks into a tiny blob when touched
- Green hydra get their color from algae living inside them
Similar species
Plumatella bryozoans have horseshoe or crown shaped feathery tentacles on tubes rather than a single stalk. Rotifer colonies and stalked protozoans are much smaller.
Profile
| Season | Spring through fall, booming when zooplankton are abundant. |
|---|---|
| Starts | Most active above about 55 F |
| Light | Green hydra need light |
| Depth | Shallow plant beds |
| How it spreads or reproduces | Budding off new hydra; resting eggs survive winter |
| Habitat | Plants, rocks and debris in clean ponds, lakes and slow streams; also in aquariums and hatchery tanks. |
Why it matters in a lake
Harmless to people. They catch zooplankton and tiny larvae with stinging tentacles and can kill fish fry in hatchery tanks and small rearing ponds.
Where it is found
- Idaho: Common
- Oregon: Common
- Wyoming: Common
Classification
| Kingdom | Animalia |
|---|---|
| Phylum | Cnidaria |
| Class | Hydrozoa |
| Order | Anthoathecata |
| Family | Hydridae |
| Scientific name | Hydra spp. |
Freshwater jellyfish
Daphnia (water flea)
Midge larvae (bloodworms)
Keratella (spined rotifer)
Mosquito larvaeNeed a hand?
Found it in your lake?
Send us a photo and we will identify it and tell you what it means for your lake.
Idaho / Wyoming (208) 501-4531Oregon (541) 280-0596