The dorsal side of the skin of Pheretima is brown due to

Options

A. Porphyrin
B. Melanin
C. Heparin
D. Renin

Answer

To answer the question about why the dorsal side of the skin of Pheretima (the earthworm) is brown, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Organism**: Pheretima is the scientific name for a type of earthworm. Understanding the organism helps us know what to look for in terms of pigmentation.

2. **Understand Skin Pigmentation**: The skin of many organisms, including earthworms, can have different colors due to the presence of specific pigments.

3. **Consider the Options**: The options provided are:
- Option 1: Porphyrin
- Option 2: Melanin
- Option 3: Heparin
- Option 4: Renin

4. **Evaluate Each Option**:
- **Porphyrin**: This pigment is known to contribute to the coloration of various organisms, including earthworms. It can give a brownish hue to the dorsal side of the skin.
- **Melanin**: While melanin is a common pigment found in many animals (especially mammals), it is not primarily responsible for the brown coloration in earthworms.
- **Heparin**: This is an anticoagulant substance and does not play a role in skin coloration.
- **Renin**: This is an enzyme involved in digestion and does not contribute to pigmentation.

5. **Conclusion**: Based on the evaluation, the correct answer is that the dorsal side of the skin of Pheretima is brown due to the presence of **porphyrin**.

### Final Answer:
The dorsal side of the skin of Pheretima is brown due to **porphyrin** (Option 1).

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