Choose the false statements regarding petromyzon .

Options

A. The body is devoid of scales
B. Mouth is circular and lacks jaws
C. It migrates to the ocean for spawning
D. The circulatory system is closed

Answer

To determine the false statements regarding Petromyzon (sea lamprey), we will analyze each of the provided options step by step.

### Step-by-Step Solution:

1. **Understanding Petromyzon**:
- Petromyzon is commonly known as the sea lamprey. It is a type of jawless fish that is known for its unique characteristics.

2. **Analyzing the Options**:
- **Option 1**: "The body is devoid of scales."
- True. Sea lampreys have smooth skin and lack scales. This statement is correct.

- **Option 2**: "Mouth is circular and lacks jaws."
- True. Sea lampreys have a circular mouth and do not possess jaws. This statement is also correct.

- **Option 3**: "It migrates into the ocean for spawning."
- False. Sea lampreys are known to migrate from the ocean into rivers for spawning, not the other way around. This statement is incorrect.

- **Option 4**: "The circulatory system is closed."
- True. Sea lampreys have a closed circulatory system, which is a characteristic of vertebrates. This statement is correct.

3. **Conclusion**:
- The only false statement among the provided options is: "It migrates into the ocean for spawning."

### Summary of the False Statement:
- The false statement regarding Petromyzon is that it migrates into the ocean for spawning; in reality, it migrates from the ocean into rivers for this purpose.