Scroll valve is present in

Options

A. Respiratory system of cartilaginous fishes
B. Intestine of cartilaginous fishes
C. Intestine of bony fishes
D. Respiratory system of bony fishes

Answer

**Step-by-Step Solution:**

1. **Understanding the Scroll Valve**: The scroll valve is a spiral-shaped structure that is involved in the digestive system of certain fish.

2. **Identifying the Types of Fish**: There are two main classes of fish to consider: cartilaginous fishes (class Chondrichthyes) and bony fishes (class Osteichthyes).

3. **Locating the Scroll Valve**: The scroll valve is specifically known to be present in the intestines of cartilaginous fishes. This is a key detail that distinguishes it from bony fishes.

4. **Function of the Scroll Valve**: The primary function of the scroll valve is to increase the surface area within the intestine. This increased surface area allows for more efficient absorption of nutrients from the food that the fish consumes.

5. **Conclusion**: Based on the information gathered, we can conclude that the scroll valve is present in the intestine of cartilaginous fishes.

6. **Final Answer**: The correct answer is option B: "intestine of cartilaginous fishes."

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