In which of the following animals Hb ( haemoglobin ) is found dissolved in plasma

Options

A. Earthworm
B. Cockroach
C. Planaria
D. Sepia

Answer

To solve the question of which animal has hemoglobin dissolved in plasma, we can analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Hemoglobin**: Hemoglobin is a red pigment found in blood that is responsible for transporting oxygen. It can either be dissolved in plasma or contained within red blood cells.

2. **Analyzing the Options**:
- **Earthworm**: Earthworms have a closed circulatory system. In this system, blood flows through vessels. The blood plasma of earthworms is red due to the presence of hemoglobin, which is dissolved in the plasma. Therefore, hemoglobin is indeed found dissolved in the plasma of earthworms.
- **Cockroach**: Cockroaches have an open circulatory system where the blood (called hemolymph) is not contained in vessels but flows freely in the body cavity. Hemolymph is colorless because it lacks hemoglobin, so this option does not apply.
- **Planaria**: Planaria belong to the phylum Platyhelminthes and do not have a circulatory system. As a result, they do not possess hemoglobin, making this option incorrect.
- **Sepia (Cuttlefish)**: Sepia belongs to the phylum Mollusca and contains hemocyanin, which is a different respiratory pigment that gives their blood a blue color. They do not have hemoglobin, so this option is also incorrect.

3. **Conclusion**: Based on the analysis, the only animal from the options provided that has hemoglobin dissolved in plasma is the **Earthworm**.

### Final Answer:
**Earthworm** is the correct answer.

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