Primary function of protonephridia

Options

A. Excretion
B. Ionic and fluid volume regulation
C. Eutely
D. None

Answer

### Step-by-Step Solution:

1. **Understanding Protonephridia**:
- Protonephridia are excretory structures found in certain invertebrates, particularly in the phylum Platyhelminthes (flatworms).
- They are a network of tubules that help in the removal of waste products from the body.

2. **Primary Function**:
- The primary function of protonephridia is **excretion**. They help in the elimination of metabolic waste products from the organism's body.

3. **Location**:
- Protonephridia are primarily found in organisms belonging to the phylum Platyhelminthes, which includes flatworms such as planarians, flukes, and tapeworms.

4. **Comparison with Other Functions**:
- While protonephridia may have some role in ionic and fluid volume regulation, this function is not as pronounced in Platyhelminthes compared to higher organisms.
- Other functions mentioned, such as Euteli, pertain to body segment development and are not directly related to the primary function of protonephridia.

5. **Conclusion**:
- Based on the above points, the correct answer to the question regarding the primary function of protonephridia is **excretion**.