Which of the following feature is common among Nereis, Pheretima and Hirudinaria?

Options

A. Well developed clitellum for cocoon formation
B. Chitinous setae and parapodia for locomotion
C. Open circulatory system called haemocoel
D. Coelomate and metamerically segmented animals

Answer

To solve the question regarding the common feature among Nereis, Pheretima, and Hirudinaria, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding the Organisms**:
- **Nereis**: A genus of polychaete worms, commonly known as ragworms, which are marine and have parapodia.
- **Pheretima**: Commonly known as earthworms, which are terrestrial and belong to the class Oligochaeta.
- **Hirudinaria**: Commonly known as leeches, which are also annelids but belong to the class Hirudinea.

2. **Analyzing the Options**:
- **Option 1: Well-Developed Clitellum for Cocoon Formation**:
- The clitellum is present in Pheretima (earthworms) and Hirudinaria (leeches) for cocoon formation, but it is absent in Nereis. Therefore, this option is incorrect.

- **Option 2: Chitinous Setae and Parapodia for Locomotion**:
- Parapodia are present in Nereis but absent in Pheretima and Hirudinaria. Chitinous setae are found in both Pheretima and Hirudinaria but not in Nereis. Thus, this option is also incorrect.

- **Option 3: Open Circulatory System (Hemocoel)**:
- Nereis has an open circulatory system, while Pheretima and Hirudinaria possess a closed circulatory system. Therefore, this option is incorrect.

- **Option 4: Coelomates and Metamerically Segmented Animals**:
- All three organisms (Nereis, Pheretima, and Hirudinaria) are coelomates (having a true coelom) and exhibit metameric segmentation (body divided into segments). This option is correct.

3. **Conclusion**:
- The common feature among Nereis, Pheretima, and Hirudinaria is that they are all coelomates and metamerically segmented animals. Therefore, the correct answer is **Option 4**.