Which one assist in locomotion ?

Options

A. Cnidoblasts in obelia
B. Posterior sucker in Hirudinaria
C. Trichocysts in Paramecium
D. Clitellum in Pheretima

Answer

To determine which structure assists in locomotion among the given options, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding the Options**:
- We have four options to consider: Nidoblast, Posterior Sucker in Hirudinia, Trichocyst in Paramecium, and Sleutelum of Ferritima.

2. **Analyzing Nidoblast**:
- Nidoblast is a type of cell found in Cnidarians.
- Its primary function is to release toxins for defense and prey capture, not for locomotion.
- **Conclusion**: Nidoblast does not assist in locomotion.

3. **Analyzing Posterior Sucker in Hirudinia**:
- Hirudinia refers to a class of Annelida, commonly known as leeches.
- The posterior sucker creates a vacuum that allows the leech to attach to surfaces and move by looping its body.
- This looping movement is a form of locomotion.
- **Conclusion**: The posterior sucker assists in locomotion.

4. **Analyzing Trichocyst in Paramecium**:
- Trichocysts are needle-shaped structures in Paramecium.
- They are primarily used for defense and capturing food, not for movement.
- **Conclusion**: Trichocyst does not assist in locomotion.

5. **Analyzing Sleutelum of Ferritima**:
- The Sleutelum is a copulatory organ in certain annelids.
- Its function is related to reproduction and sexual processes, not movement.
- **Conclusion**: Sleutelum does not assist in locomotion.

6. **Final Conclusion**:
- After analyzing all options, the only structure that assists in locomotion is the **Posterior Sucker in Hirudinia**.

### Answer:
The structure that assists in locomotion is the **Posterior Sucker in Hirudinia**.

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