Which among the following is the onl vertebrate osmoconformer

Options

A. Rabbit
B. Hagfish
C. Bird
D. None of these

Explanation

### Step-by-Step Solution:

1. **Understanding the Terms**: Begin by defining the terms "osmoconformer" and "osmoregulator". Osmoconformers are organisms that cannot maintain a constant osmolarity and instead adjust their internal osmolarity to match their external environment. Osmoregulators, on the other hand, can maintain a stable internal osmolarity regardless of external conditions.

2. **Identifying Characteristics**: Recognize the characteristics of osmoconformers. They adapt their body fluid osmolarity based on the surrounding environment. For instance, if the external environment has lower osmolarity, they will lose solutes and dilute their body fluids. Conversely, if the external environment has higher osmolarity, they will gain solutes.

3. **Vertebrate Classification**: Understand that most vertebrates are osmoregulators, meaning they actively maintain their internal osmolarity. This is crucial for their survival in varying environments.

4. **Finding the Exception**: Since the question asks for the only vertebrate osmoconformer, we need to identify the exception among vertebrates.

5. **Conclusion**: The only vertebrate that acts as an osmoconformer is the hagfish. Therefore, the answer to the question is hagfish.

### Final Answer:
The only vertebrate osmoconformer is the **hagfish**.

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