Hydras typically prey on flatworms, crustaceans and aquatic insects. Hydras are small, aquatic invertebrates that somewhat resemble jellyfish. Most are largely sessile organisms, that attach themselves to the substrate for extended periods of time.
Hydras are almost entirely carnivorous. They capture prey, such as worms, aquatic insects and copepods, with their tentacles. The tentacles grab the food item and then discharge small, venomous barbs called nematocysts into the prey. Once incapacitated, the animal is pulled towards the hydra’s mouth, called the proctostome.
Hydras have few defenses against predators. The nematocysts dissuade some predators, but the primary means by which the species survives is their high reproductive rate. Hydra reproduce asexually by a process known as budding. The species naturally goes through yearly population fluctuations. Populations are highest in the early summer and they begin to decline shortly thereafter.
Hydras move by a technique called basal gliding, in which the base slides over the substrate. Alternatively, hydras can flip through the water column to move. Scientists note that the movements of hydra often seem to be inconsistent with a given stimuli. In general, the movements of the small creatures appear mechanical and independent of the movements in other parts of their bodies.