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 solve the question regarding the correct statement about Cyclostomata, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Cyclostomata**: Cyclostomata are a group of jawless fish that include species like lampreys and hagfish. They are characterized by their unique mouth structure and lack of jaws.

2. **Identify Key Characteristics**:
- **Jawless**: Cyclostomata do not possess jaws, which distinguishes them from other fish.
- **Mouth Structure**: They have a sucking, circular mouth that is adapted for their feeding habits.
- **Gill Slits**: Cyclostomata have multiple pairs of gill slits, typically ranging from 6 to 15 pairs.

3. **Evaluate the Options**:
- **Option 1**: "All living members are endoparasite on some fishes." This is incorrect because Cyclostomata are primarily ectoparasites, meaning they attach to the outside of other fish.
- **Option 2**: "They have an elongated body bearing 2 pair of gill slits." This is also incorrect as they have 6 to 15 pairs of gill slits.
- **Option 3**: "They have a sucking in circular mouth without jaws." This statement is correct as it accurately describes their mouth structure.

4. **Conclusion**: Based on the evaluation of the options, the correct statement about Cyclostomata is that they have a sucking, circular mouth without jaws.

### Final Answer:
The correct statement about Cyclostomata is: **They have a sucking in circular mouth without jaws.**

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