Hydra
Hydra (a genus, not a single species; common species include H. vulgaris, H. viridissima, H. oligactis)
- Order & Family
- Order Anthoathecata, Family Hydridae (though sometimes classified under the order Hydrida within the class Hydrozoa)
- Size
- Typically 1 to 30 mm in length when extended, with tentacles that can extend much further.
Natural Habitat
Freshwater environments, including ponds, lakes, and slow-moving streams. They typically attach to aquatic vegetation, rocks, or submerged debris.
Diet & Feeding
Carnivorous, primarily feeding on small aquatic invertebrates like Daphnia, cyclops, and other small crustaceans and larval insects.
Behavior Patterns
Hydras are sessile (immobile) polyps that attach to substrates with a basal disc. They can move slowly by looping or somersaulting. They are ambush predators, extending their tentacles to capture prey. Reproduction can be asexual (budding) or sexual. They have remarkable regenerative capabilities.
Risks & Benefits
Hydras are not harmful to humans. In aquatic ecosystems, they play a role in the food web as predators of small invertebrates. In aquariums, they can sometimes become a nuisance by competing with or preying on very small fry or shrimp larvae, but their presence generally indicates good water quality.