Blue-coloured pigment present in the blood of molluscs is known as:

Options

A. hemocyanin
B. hemerythrin
C. hemoglobin
D. phytochromes

Answer

**Step-by-Step Solution:**

1. **Identify the Context**: The question asks about a specific blue-colored pigment found in the blood of molluscs.

2. **Understand the Role of Pigments**: In many animals, pigments in the blood are responsible for transporting oxygen. In molluscs, the pigment that serves this function is different from that in vertebrates.

3. **Recognize the Key Pigments**:
- **Haemocyanin**: This is the blue pigment found in the blood of molluscs. It contains copper ions, which give it the blue color.
- **Haemoglobin**: Found in vertebrates, this pigment contains iron and gives red coloration to the blood.
- **Haemoerythrin**: Another iron-containing pigment, but it is found in some marine invertebrates and also appears reddish.
- **Phytochromes**: These are not found in animals; they are pigments in plants that respond to light.

4. **Conclude the Answer**: Based on the information, the blue-colored pigment present in the blood of molluscs is known as **haemocyanin**.

**Final Answer**: The blue-colored pigment present in the blood of molluscs is known as **haemocyanin**.

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