Which one is true statements with reference to cnidoblast cell in coelenterates ?

Options

A. Can be used again and again
B. Abundant on basel disc
C. They are endodermal
D. None of these

Answer

To determine the true statement regarding cnidoblast cells in coelenterates, we can analyze the information provided step by step.

### Step-by-Step Solution:

1. **Understanding Cnidoblast Cells**: Cnidoblasts, also known as cnidocytes, are specialized cells found in coelenterates (like jellyfish, corals, and sea anemones). They are primarily responsible for capturing prey and defense.

2. **Function of Cnidoblasts**: These cells contain a structure called a nematocyst, which is a stinging organelle. When triggered, the nematocyst releases a toxin that can immobilize or kill prey. This toxin is referred to as hypnotoxin.

3. **Regeneration of Cnidoblasts**: Cnidoblasts can only be used once. After they discharge their nematocyst to capture prey or defend against threats, they undergo a process called phagocytosis, where they are broken down and dissolved outside the body.

4. **Location of Cnidoblasts**: Cnidoblasts are not abundant on the basal disc of coelenterates. Instead, they are primarily found in the tentacles and around the mouth area (hypostome). This is because their elongated structure allows them to function effectively in these regions for capturing prey.

5. **Origin of Cnidoblasts**: Cnidoblasts are derived from the epidermis, not the endoderm. They are part of the outer layer of cells in coelenterates.

6. **Evaluating Statements**: Based on the above points, we can conclude that:
- Cnidoblasts can only be used once.
- They are found in the tentacles and hypostome, not the basal disc.
- They are derived from the epidermis, not the endoderm.

Since all the provided statements in the question are incorrect based on our analysis, the correct conclusion is that none of the statements about cnidoblasts in coelenterates are true.

### Final Answer:
None of the statements regarding cnidoblast cells in coelenterates are true.

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