What are setae? Give their function.

Explanation

**Step-by-Step Solution:**

1. **Definition of Setae**: Setae are F-shaped chitinous structures found on the ventral side of earthworms. They are present in each segment of the earthworm's body.

2. **Function of Setae**: The primary function of setae is to aid in locomotion. They help the earthworm to move by anchoring the body to the substrate and allowing for movement in a forward or backward direction.

3. **Mechanism of Movement**: The movement of earthworms is referred to as peristaltic movement. This involves the contraction and relaxation of muscles in conjunction with the movement of setae. The setae extend and retract in a circular or ring-like motion, which facilitates the movement of the earthworm.

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