Cnidae are essentially the defining feature of cnidarians, characterized as organelle-like capsules containing eversible tubules that can be shot outwards.
Understanding Cnidae
Cnidae are crucial structures found in all cnidarians (like jellyfish, corals, and sea anemones) and are responsible for various functions, including prey capture, defense, and locomotion. A key characteristic is their eversible tubule, meaning it can be turned inside out and rapidly projected outwards. No cnidarian species is known to have lost the ability to produce cnidae.
Types of Cnidae
While there are many variations, the three main types of cnidae are:
- Nematocysts: These are stinging organelles and perhaps the most well-known type. They are used to inject venom into prey or potential threats.
- Ptychocysts: These are used for building tubes in which some cnidarians live.
- Spirocysts: These are used for adhesion.
| Type | Function | Example |
|---|---|---|
| Nematocysts | Stinging and defense | Jellyfish stinging cells |
| Ptychocysts | Tube construction | Anemone tube building |
| Spirocysts | Adhesion/entanglement | Coral capturing prey |
In summary, cnidae are complex organelles, diagnostic of the phylum Cnidaria, used for a variety of functions through the rapid eversion of their tubules.
