Talk:Cnidaria
From Academic Kids
These two paragraphs seem to lack continuity, and redefine the stinging cells from cnidocysts to nematocysts. Other literature e.g. the tree of life page states that nematocysts are one kind of cnidae, albeit the commonest (the term cnidocsyst is widely used as well).
- Cnidarians lack organs, but have various differentiated tissues. Their movement is coordinated by a decentralized nerve net and simple receptors. Respiration takes place by diffusion of oxygen directly through their tissues, without specialized structures like gills, tracheae or lungs, made possible by their small or flattened bodies. Tentacles surrounding the mouth contain cnidocysts, specialized stinging cells. The ability to sting is what gives cnidarians their name (Greek knide, nettle).
- Cnidarians use special means in capturing their prey. They use nematocysts which are stinging cells that are used to render their prey unable to defend themselves. The nematocysts are the Cnidarians main form of defense. Cnidarians administer the stinging cells when they are able to sense chemically or physically the presence of another entity. Dead or paralyzed prey are pushed into the cnidarian's mouth by the tentacles. Digestion occurs in the gastrovascular cavity, and any undigested food exits the body via the mouth.
joe 20:54, 20 Jul 2004 (UTC)
