Peristalsis of alimentary canal occurs independent of the contraction and relaxation of body wall in

Options

A. acoelomates
B. pseudocoelomates
C. eucoelomates
D. both (2) and (3)

Answer

To solve the question regarding peristalsis of the alimentary canal occurring independent of the contraction and relaxation of the body wall, we will analyze the three categories of animals provided: Acoelomates, Pseudocoelomates, and Coelomates (Ucoelomates).

### Step-by-Step Solution:

1. **Understanding Acoelomates**:
- Acoelomates are animals that lack a true body cavity (coelom). They do not have a proper digestive tract.
- Since they lack a digestive tract, peristalsis, which is the wave-like muscle contractions that move food through the digestive system, cannot occur in these organisms.
- **Conclusion**: Acoelomates do not exhibit peristalsis.

2. **Understanding Pseudocoelomates**:
- Pseudocoelomates have a false coelom, which means they possess a body cavity that is not completely lined with mesoderm. An example of pseudocoelomates is nematodes (roundworms).
- Nematodes have a well-developed digestive tract and exhibit peristalsis due to the presence of muscles that contract and relax.
- **Conclusion**: Pseudocoelomates do exhibit peristalsis.

3. **Understanding Coelomates (Ucoelomates)**:
- Coelomates have a true coelom, which is a body cavity fully lined with mesoderm. They also possess a complete digestive tract.
- In coelomates, peristalsis occurs as well, facilitated by the coordinated contraction and relaxation of muscles in the body wall.
- **Conclusion**: Coelomates also exhibit peristalsis.

4. **Final Analysis**:
- The question specifically asks for the occurrence of peristalsis independent of the contraction and relaxation of the body wall.
- Since both pseudocoelomates and coelomates exhibit peristalsis that relies on muscle contractions, the correct answer must be Acoelomates, as they do not have a digestive tract where peristalsis can occur.

### Answer:
**Acoelomates** (Option A) is the correct answer, as peristalsis does not occur in these organisms due to the absence of a digestive tract.