A distinctive feature of Aschelminthes is

Options

A. incomplete gut
B. flame cells
C. muscular pharynx
D. pseudocoelom

Answer

### Step-by-Step Solution:

1. **Understanding Aschelminthes**: Aschelminthes, also known as pseudocoelomates, are a group of worms characterized by their unique body structure and features.

2. **Body Structure**: The body of Aschelminthes is circular in shape. This is an important aspect of their morphology.

3. **Habitat**: Aschelminthes can be either free-living or parasitic. However, many species within this group are predominantly parasitic.

4. **Tissue Layers**: They are classified as triploblastic organisms, meaning they have three germ layers: ectoderm, mesoderm, and endoderm.

5. **Body Cavity**: A distinctive feature of Aschelminthes is that they are pseudocoelomates. This means they have a body cavity (pseudocoel) that is not completely lined by mesodermal tissue, which is a unique characteristic compared to true coelomates.

6. **Body Covering**: The body of Aschelminthes is covered with a cuticle, which provides protection and helps in their survival in different environments.

7. **Digestive System**: They possess a complete digestive system, which means they have a mouth and an anus, allowing for a more efficient digestion process.

8. **Reproductive System**: Aschelminthes have separate sexes, indicating that they reproduce sexually.

9. **Excretory System**: Their excretory system consists of renette glands, which are involved in osmoregulation and excretion.

10. **Fertilization and Development**: Fertilization in Aschelminthes is internal, and their development can be either direct or indirect.

11. **Identifying the Distinctive Feature**: Among the various features discussed, the pseudocoelomate structure is the only distinctive feature that sets Aschelminthes apart from other groups like Platyhelminthes and Annelids.

12. **Conclusion**: Therefore, the distinctive feature of Aschelminthes is that they are pseudocoelomates.

### Final Answer:
The distinctive feature of Aschelminthes is that they are **pseudocoelomates**.

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