Hydra are multi-cellular organisms. They are made up of two layers of epithelial cells and have a hypostome or mouth opening. Circling the mouth are tentacles that contain nematocysts or … See more

Although Hydra are sessile, they can move in short bursts. An individual can extend and contract with a mixture of muscle movement and water (hydraulic) pressure created inside the digestive cavity. Tiny cells … See more

H. viridissima is currently the only known Hydra species that has a permanent symbiotic relationship with photosynthetic unicellular See more

Hydra are capable of escaping death by renewing their body tissues. Mortality rates are extremely low and there have been no signs of decline in reproductive rate. See more

Hydra cannot be found in impaired water due to their low tolerance to pollution. They can be used to rank toxicants on level of potential hazard. The simple tubular body and … See more

Hydra are typically hermaphroditic or gonochoric. Uniquely to Hydra, the medusa stage is absent and only the polyps will reproduce sexually and asexually. H. viridissima will reproduce sexually when temperatures have warmed to at least 20 °C, … See more