Which of the following statements is correct about cyclostomata ?

Options

A. All living members are endoparasites on some fishes.
B. They have an elongated body bearing 2 pair of gill slits
C. They have a sucking and circular mouth without jaws .
D. All of the above.

Answer

To determine which statement is correct about cyclostomata, let's analyze the options step by step.

### Step 1: Understanding Cyclostomata
Cyclostomata is a class of jawless fish that belong to the phylum Chordata and the subphylum Vertebrata. They are characterized by their circular mouths and lack of jaws.

### Step 2: Analyzing the Statements
1. **Statement A**: "All living members are endoparasites on some fishes."
- This statement is incorrect. Cyclostomata, such as lampreys, are primarily ectoparasites, meaning they attach to the outside of their host fish to feed.

2. **Statement B**: "They have an elongated body bearing two pairs of gill slits."
- This statement is also incorrect. Cyclostomata have an elongated body, but they possess 6 to 15 pairs of gill slits, not just two.

3. **Statement C**: "They have a circular and sucking mouth without jaws."
- This statement is correct. Cyclostomata have a circular mouth that is adapted for sucking and they do not have jaws.

4. **Statement D**: "All of the above."
- Since statements A and B are incorrect, this statement is also incorrect.

### Conclusion
The correct statement about cyclostomata is **Statement C**: "They have a circular and sucking mouth without jaws."

### Final Answer
The correct answer is **C**.

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