Nephrostome occurs in Earthworm

Options

A. Septal nephridia
B. Integumentary nephridia
C. Pharyngeal and septal nephridia
D. Pharyngeal and integumentary nephridia

Answer

### Step-by-Step Solution:

1. **Understanding Nephrostome**: The nephrostome is a structure associated with the excretory system in certain organisms, including earthworms. It is a part of the nephridia, which are the excretory organs.

2. **Identifying Types of Nephridia in Earthworms**: Earthworms have different types of nephridia, including:
- Septal Nephridia
- Integumentary Nephridia
- Pharyngeal Nephridia

3. **Location of Septal Nephridia**: Septal nephridia are located in the inter-segmental septum, specifically between the 15th and 16th segments of the earthworm. This positioning is crucial for understanding where nephrostomes are found.

4. **Structure of Septal Nephridia**: Each septal nephridium consists of several parts:
- **Nephrostome**: The ciliated funnel-shaped structure that opens into the coelom.
- **Neck**: Connects the nephrostome to the body of the nephridium.
- **Body**: The main part of the nephridium.
- **Terminal Duct**: Leads to the exterior for excretion.

5. **Function of Nephrostome**: The nephrostome functions to collect coelomic fluid, which contains waste products, and is essential for the excretory process.

6. **Conclusion**: Based on the information, the nephrostome occurs in septal nephridia, and not in integumentary nephridia. Therefore, the correct answer to the question is "septal nephridia".

### Final Answer:
The nephrostome occurs in **septal nephridia** of the earthworm.

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