Petromyzon is

Options

A. Anadromous
B. Catadromous
C. Nondromous
D. Potamodormous

Answer

### Step-by-Step Solution:

1. **Understanding Petromyzon**:
- Petromyzon is commonly known as lamprey and belongs to the class Cyclostomata. Cyclostomes are characterized by their round or spherical mouths and lack of jaws.

2. **Identifying Migration Types**:
- The question revolves around the type of migration exhibited by Petromyzon. There are several types of fish migrations:
- **Anadromous**: Fish that migrate from saltwater to freshwater to breed.
- **Catadromous**: Fish that migrate from freshwater to saltwater to breed.
- **Non-adromous**: Fish that do not migrate at all.
- **Potamodromous**: Fish that migrate within freshwater environments.

3. **Determining the Migration of Petromyzon**:
- Petromyzon (lamprey) is known to migrate from marine environments (like seas or lakes) to freshwater environments (like rivers) for breeding purposes. This behavior classifies them as anadromous.

4. **Evaluating Other Options**:
- **Catadromous**: This is not applicable as it refers to fish moving from freshwater to saltwater.
- **Non-adromous**: This is incorrect because Petromyzon does migrate.
- **Potamodromous**: This refers to migration within freshwater, which does not apply to Petromyzon.

5. **Conclusion**:
- Based on the definitions and the behavior of Petromyzon, the correct answer is that Petromyzon is anadromous.

### Final Answer:
Petromyzon is an **anadromous** fish.

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