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HomeEducationCoralsWhat are Corals?

# Nematocyst Cell

The diagram above  shows the anatomy of a nematocyst cell and its “firing” sequence, from  left to right. On the far left is a nematocyst inside its cellular  capsule. The cell’s thread is coiled under pressure and wrapped around  a stinging barb. When potential prey makes contact with the tentacles  of a polyp, the nematocyst cell is stimulated. This causes a flap of  tissue covering the nematocyst—the operculum—to fly open. The middle  image shows the open operculum, the rapidly uncoiling thread and the  emerging barb. On the far right is the fully extended cell. The barbs  at the end of the nematocyst are designed to stick into the polyp’s  victim and inject a poisonous liquid. When subdued, the polyp’s  tentacles move the prey toward its mouth and the nematocysts recoil  back into their capsules.

### Corals Lessons

              - Welcome
              - What are Corals?
              - Zooxanthellae What's That?
              - How Do Stony Corals Grow?
              - How Do Coral Reefs Form?
              - Where Are Coral Reefs Found?
              - How Do Corals Reproduce?
              - Importance of Coral Reefs
              - Natural Threats to Coral Reefs
              - Anthropogenic Threats to Corals
              - Coral Diseases
              - Protecting Coral Reefs
              - References
              - Roadmap to Resources 
              - Subject Review (PDF)

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