All the following statements are correct about Petromyzon (Lamprey), except

Options

A. Lampreys are marine and migrate for spawning into rivers (Anadromous)
B. Their characteristic ammocoete larvae after matamorphosis migrates back to the ocean
C. After spawing the adult lamprey stops feeding and migrates back to ocean where it lives
D. It is a sanguivorous ectoparasite on other fishes

Answer

To solve the question regarding Petromyzon (Lamprey) and identify the incorrect statement, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Lamprey Characteristics**:
- Lampreys are jawless fishes belonging to the order Petromyzontiformes and the superclass Cyclostomata. They are known for their unique features, such as a toothed, funnel-like sucking mouth.

2. **Analyze the Statements**:
- We need to evaluate each statement provided in the question to determine which one is incorrect.

3. **Evaluate the First Statement**:
- **Statement**: "Lampreys are marine and migrate for spawning into rivers."
- **Analysis**: This is true. Lampreys are indeed marine creatures that migrate to freshwater rivers to spawn, which is characteristic of anadromous species.

4. **Evaluate the Second Statement**:
- **Statement**: "Their characteristic ammocoete larva after metamorphosis migrates back to the ocean."
- **Analysis**: This is also true. The ammocoete larva, after undergoing metamorphosis, migrates back to saltwater.

5. **Evaluate the Third Statement**:
- **Statement**: "After spawning, the adult lamprey stops feeding and migrates back to the ocean where it lives."
- **Analysis**: This statement is incorrect. After spawning, adult lampreys do not migrate back to the ocean to live; instead, they typically die after spawning.

6. **Evaluate the Fourth Statement**:
- **Statement**: "Sanguivorous ectoparasite on other fishes."
- **Analysis**: This is true. Lampreys are known to be sanguivorous ectoparasites, feeding on the blood of other fish.

7. **Conclusion**:
- The incorrect statement about Petromyzon (Lamprey) is: "After spawning, the adult lamprey stops feeding and migrates back to the ocean where it lives."

### Final Answer:
The incorrect statement about Petromyzon (Lamprey) is: "After spawning, the adult lamprey stops feeding and migrates back to the ocean where it lives."

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