Hydra Fusca polyp in my Aquarium.

This video is taken with my Canon EOS 1000D. I set it up for remote shooting and captured my screen. Sometimes the video gets really blurry because I had to use manual focus. Also the video speed is 2 times the normal speed. Hydra is included in the phylum Cnidaria, along with sea anemones, jellyfish and coral polyps, and is one of the few freshwater members of this group. One feature all members of the Cnidaria have in common is the possession of thread cells or cnidia or nematocysts -- tiny stinging cells located in the body and tentacles which discharge a paralyzing poison into prey organisms, enabling their capture and ingestion. The nematocysts of Hydra are similar to those of the marine stinging jellyfish which periodically invade beaches, causing injury and sometimes death to humans. The Hydra's body is a hollow tube consisting of two layers of cells separated by an unstructured gelatinous layer. The outer, clear layer of cells is called the epidermis or ectoderm, and generates the nematocysts. The inner layer is called the endoderm or gastrodermis, and produces the enzymes which digest the Hydra's food. The separating layer is called the mesoglea. It is a gel of various secretions and proteins, containing loose cells not organised into any kind of tissue. The Hydra's tentacles are hollow, tubular extensions of these three layers. Many members of the Cnidaria establish symbiotic relationships with zoochlorellae which impart a green colour to the polyp. Coral polyps are a well known example of this in the marine environment, and in fresh water, the best known example is Hydra viridis. Hydra reproduces asexually most of the time by a process of budding, young polyps becoming detatched from the parent when they are fully developed. Seasonal episodes of sexual reproduction also occur, mature polyps developing gonads on the external body wall. Fertilized eggs give rise to tiny planula larvae which swim away, attatch themselves and develop into polyps which continue to reproduce by budding.