Signet ring stage is found in

Options

A. Plasmodium
B. Pelomyxa
C. Paramoecium
D. Euglena.

Answer

**Step-by-Step Solution:**

1. **Understanding the Signet Ring Stage**: The signet ring stage is a specific developmental phase in certain protozoan organisms, particularly in the lifecycle of Plasmodium, the causative agent of malaria.

2. **Identifying the Organism**: Plasmodium is a genus of parasitic protozoa that includes several species responsible for malaria, such as Plasmodium vivax, Plasmodium ovale, Plasmodium falciparum, and Plasmodium malariae.

3. **Lifecycle of Plasmodium**: When a female Anopheles mosquito bites a human, it injects sporozoites into the bloodstream. These sporozoites travel to the liver, where they multiply and eventually release merozoites into the bloodstream.

4. **Stages of Development**: The merozoites infect red blood cells (RBCs) and undergo several stages:
- **Trophozoite Stage**: The parasite consumes the cytoplasm of the RBC and grows.
- **Signet Ring Stage**: This follows the trophozoite stage, characterized by the appearance of a contractile vacuole that pushes the cytoplasm to the periphery of the cell, giving it a distinctive ring-like appearance.
- **Amoeboid Stage**: After the signet ring stage, the parasite further develops into the amoeboid stage.

5. **Conclusion**: Based on the information, the signet ring stage is specifically associated with Plasmodium. Therefore, the correct answer to the question is that the signet ring stage is found in **Plasmodium**.

**Final Answer**: The signet ring stage is found in **Plasmodium**.

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