In earthworm, small fleshy lobe hung over mouth is known as

Options

A. Peristomium
B. Nephridiospores
C. Clitellum
D. Prostomium

Explanation

**Step-by-Step Solution:**

1. **Understanding Earthworm Anatomy**: Begin by recognizing that the earthworm's body is segmented, typically consisting of 100 to 120 segments.

2. **Identifying Key Structures**: Focus on the anterior end of the earthworm where the mouth is located. The mouth is situated in the first segment, which is also referred to as the peristomium.

3. **Defining the Prostomium**: The small fleshy lobe that hangs over the mouth is known as the prostomium. This structure is distinct from the mouth itself.

4. **Functions of the Prostomium**: The prostomium serves multiple functions:
- It aids in the opening of cracks in the soil as the earthworm moves.
- It has sensory functions, helping the earthworm to navigate its environment.

5. **Evaluating Options**: If presented with multiple-choice options:
- Peristomium: Incorrect, as this refers to the mouth.
- Nephridiospores: Incorrect, as this is unrelated to the mouth structure.
- Clitellum: Incorrect, as this is a different part of the earthworm.
- Prostomium: Correct, as this is the small fleshy lobe over the mouth.

6. **Conclusion**: Therefore, the small fleshy lobe that hangs over the mouth of the earthworm is called the **prostomium**.

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