In which segment is the mouth located in earthworm?

Explanation

To determine the segment in which the mouth is located in an earthworm, follow these steps:

1. **Identify the Orientation of the Earthworm**: Understand that the earthworm has two ends - the anterior (front) end and the posterior (back) end. The mouth is located at the anterior end.

2. **Locate the Mouth and Prostomium**: The mouth of the earthworm is not just a simple opening; it is accompanied by a structure called the prostomium. The prostomium is a lobe-like structure that covers the mouth and helps the earthworm in its movement through soil.

3. **Determine the Segment Number**: The mouth and the prostomium are located in the first segment of the earthworm. This segment is specifically referred to as the peristomium.

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