Asymmetry develops due to torsion in mollusc

Options

A. Octopus
B. Pila
C. Teredo
D. Dentallium

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which mollusk exhibits asymmetry due to torsion. Torsion is a specific developmental process that occurs in certain mollusks.

2. **Identifying the Options**: The options provided are:
- a) Octopus
- b) Pyla
- c) Pteridohio
- d) Dentalium

3. **Defining Torsion**: Torsion is a developmental process where the body of the mollusk undergoes a 180-degree twist. This results in the asymmetrical arrangement of the body parts.

4. **Analyzing Each Option**:
- **Octopus**: This is a soft-bodied, eight-limbed mollusk. It does not undergo torsion, hence does not exhibit asymmetry due to this process.
- **Pyla**: This belongs to the class of gastropods, which are known to undergo torsion during their development, leading to asymmetry.
- **Pteridohio**: Commonly known as the noble shipworm, it is a bivalve mollusk and does not undergo torsion.
- **Dentalium**: Known as tusk shells, these are also marine mollusks that do not exhibit torsion.

5. **Conclusion**: Based on the analysis, the correct answer is **b) Pyla**, as it is the only option that undergoes torsion, leading to asymmetry.