Protonephridia or flame cells or solenocytes are the excretory structures in

Options

A. platyhelminthes/flatworms
B. rotifers and some annelids
C. cephalochordate(branchiostoma)
D. all of the above

Explanation

To answer the question regarding the excretory structures known as protonephridia, flame cells, or solenocytes, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Terms**:
- Protonephridia, flame cells, and solenocytes are all terms used to describe a specific type of excretory system found in certain organisms.

2. **Identifying the Organisms**:
- These structures are primarily found in invertebrates, particularly in flatworms (Platyhelminthes), such as planarians, as well as in some other groups like rotifers and certain annelids.

3. **Function of Protonephridia**:
- Protonephridia function in osmoregulation and excretion. They help in the removal of waste products and excess water from the body.

4. **Structure of Protonephridia**:
- Protonephridia consist of a network of tubules that end in specialized cells called flame cells or solenocytes. These cells have cilia that create a current to draw in waste and excess fluids.

5. **Conclusion**:
- Therefore, protonephridia, flame cells, or solenocytes are the excretory structures found in flatworms and some other invertebrates.

### Final Answer:
Protonephridia or flame cells or solenocytes are the excretory structures in flatworms (Platyhelminthes) and some other invertebrates.