Which one of the following statge of malarial parasite is not found in the vector

Options

A. Ookinete
B. Sporozoite
C. Merozoite
D. Zygote.

Answer

To solve the question "Which one of the following stages of the malarial parasite is not found in the vector?", we will analyze the life cycle of the malarial parasite and identify the stages present in the mosquito vector.

### Step-by-Step Solution:

1. **Understanding the Life Cycle of Malarial Parasite**:
- The malarial parasite (Plasmodium) requires two hosts to complete its life cycle: the female Anopheles mosquito (vector) and humans.

2. **Identifying the Stages of the Malarial Parasite**:
- The main stages of the malarial parasite include:
- **Gametocytes**: These are the sexual forms of the parasite found in the human host.
- **Zygote**: Formed in the mosquito's stomach when male and female gametocytes fuse.
- **Ookinete**: The motile form that develops from the zygote and invades the mosquito's midgut wall.
- **Oocyst**: The ookinete develops into an oocyst in the midgut wall, which eventually ruptures to release sporozoites.
- **Sporozoite**: The infective stage that migrates to the salivary glands of the mosquito.

3. **Analyzing Each Option**:
- **A. Ookinete**: Present in the mosquito as it develops from the zygote.
- **B. Sporozoite**: Present in the mosquito as it is released from the oocyst and migrates to the salivary glands.
- **C. Merozoite**: This stage is not found in the mosquito; it is formed in the human host after the sporozoites infect the liver and then enter the bloodstream.
- **D. Zygote**: Present in the mosquito as it is formed from the fusion of gametocytes.

4. **Conclusion**:
- The only stage that is not found in the mosquito vector is the **merozoite**. Therefore, the correct answer is option **C. Merozoite**.

### Final Answer:
**The stage of the malarial parasite that is not found in the vector is Merozoite (Option C).**