Scroll valve in Scoliodon is present in intestine and functions for

Options

A. delaying the passage of food
B. increased surface for absorption
C. respiration
D. both (1) and (2)

Answer

### Step-by-Step Solution:

1. **Identify the Organism**: The organism in question is Scoliodon, commonly known as the dogfish, which belongs to the class Chondrichthyes, known for their cartilaginous skeletons.

2. **Understand the Structure**: The scroll valve is a specific structure found in the intestine of Scoliodon. It is characterized by the inner surface of the intestine being folded into spirals.

3. **Describe the Scroll Valve**: The scroll valve consists of approximately two and a half turns of spiral folds within the intestine. This unique structure increases the surface area available for absorption.

4. **Function of the Scroll Valve**:
- **Increase Absorptive Surface**: The primary function of the scroll valve is to increase the absorptive surface area of the intestine, allowing for more efficient absorption of nutrients from digested food.
- **Delay Passage of Food**: Additionally, the scroll valve helps to slow down the passage of digested food through the intestine. This delay allows more time for nutrients to be absorbed before the food moves further along the digestive tract.

5. **Conclusion**: Therefore, the scroll valve in Scoliodon serves two main functions: it increases the surface area for absorption and delays the passage of food to enhance nutrient uptake. Both functions are essential for the efficient digestion and absorption of nutrients in this species.

### Final Answer:
The scroll valve in Scoliodon is present in the intestine and functions to both increase the absorptive surface area and delay the passage of food.

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