Hydra eat freshwater invertebrates such as small crustaceans and insect larvae. A hydra feeds by attaching itself to a fixed location, such as a leaf or branch of aquatic vegetation. It then uses its neurotoxin-lined tentacles to paralyze a prey as it approaches and then pull it into its mouth opening.
The term hydra refers to a whole genus of multi-celled freshwater polyps. Hydra are among the simplest multi-celled creatures in existence. The body structure of a hydra is no more than two cells thick at any given point. This allows for direct contact with the water for each individual cell permitting respiration and waste excretion to occur through simple diffusion with the surrounding water.
When a hydra catches one of its prey with its tentacles, the creature is paralyzed and subdued within thirty seconds. The process of ingesting the creature takes a further two minutes. Afterward, digestion will take two to three days within the body cavity of the hydra. Any solid material leftover from the digestive process is then expelled through the mouth opening.
Although lacking a brain and muscle tissue, hydra utilize a rudimentary nerve net to extend and contract the body cavity and tentacles. The nerve net functions to connect individual light-sensitive and touch-sensitive sensors located within the individual cells of the hydra.