Which type of nephridia are open and devoid of nephrostome :

Options

A. Integumentary nephridia
B. Septal nephridia
C. Pharyngeal nephridia
D. Both (2) and (3)

Answer

### Step-by-Step Solution:

1. **Understanding Nephridia**: Nephridia are the excretory organs found in earthworms (which are annelids). They help in the removal of waste from the body.

2. **Types of Nephridia**: There are three types of nephridia based on their location:
- **Integumentary Nephridia**: Located on the inner lining of the body wall.
- **Septal Nephridia**: Found on both sides of the intersegmental septa.
- **Pharyngeal Nephridia**: Present in three paired tufts at segments 4, 5, and 6.

3. **Classification Based on Opening**: Nephridia can be classified based on where they open:
- **Exonephric Nephridia**: Open directly to the outside of the body.
- **Enteronephric Nephridia**: Open into the elementary canal.

4. **Nephridiopores and Nephrostomes**:
- **Nephrostomes** are funnel-shaped, ciliated structures that help in the movement of waste material into the nephridia.
- **Nephridiopores** are openings through which waste is expelled from the body.

5. **Identifying the Types**:
- **Integumentary Nephridia**: These are exonephric and open directly to the outside through nephridiopores. They do not have nephrostomes.
- **Septal Nephridia**: These are enteronephric and open into the elementary canal, thus they have nephrostomes.
- **Pharyngeal Nephridia**: Similar to septal nephridia, they are also enteronephric and have nephrostomes.

6. **Conclusion**: The type of nephridia that are open and devoid of nephrostomes is the **Integumentary Nephridia**.

### Final Answer:
**Integumentary Nephridia**

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