Name the cell that is used for defense purposes in coelenterates

Answer

### Step-by-Step Solution:

1. **Identify the Group**: The question asks about a specific type of cell in coelenterates, which are also known as cnidarians. This group includes organisms such as jellyfish, corals, and hydras.

2. **Understand the Function**: The cells in question serve a defense purpose. They protect the organism from predators and also help in capturing prey.

3. **Name the Specialized Cells**: The specialized cells responsible for these functions are called **nidocytes**. They are also known by other names such as **nidoblast** or **nematocyte**.

4. **Explain the Mechanism**: These cells contain an organelle called a **nematocyst**, which is capable of firing a thread that releases a neurotoxin known as **hypnotoxin**. This neurotoxin can affect the central nervous system of the prey or predator, acting as a defense mechanism.

5. **Conclude with the Answer**: Therefore, the cells used for defense purposes in coelenterates are called **nidocytes**, **nidoblasts**, or **nematocytes**.

### Final Answer:
The cell that is used for defense purposes in coelenterates is called **nidocyte** (also known as **nidoblast** or **nematocyte**).

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