Which of the following phylum do not possess true coelom?

Options

A. Aschelminthes
B. Annelida
C. Ctenophora
D. Platyhelminthes

Answer

To determine which phylum does not possess a true coelom, we will analyze each of the given options step by step.

### Step 1: Understanding True Coelom
A true coelom is a fluid-filled body cavity that is completely lined by mesodermal tissue. It is important to differentiate between true coelomates, pseudocoelomates, and acoelomates.

### Step 2: Analyzing the Options
1. **Asclementis**: This phylum is characterized by the absence of a true coelom. Instead, they have a pseudocoelom, which is not fully lined by mesodermal tissue. Therefore, this option is correct as it does not possess a true coelom.

2. **Annelida**: This phylum includes segmented worms that possess a true coelom. The body cavity in annelids is lined with mesodermal tissue, making this option incorrect.

3. **Ctenophora**: Members of this phylum, commonly known as comb jellies, are also acoelomates. They do not have a true coelom, but they are not classified under the phylum that lacks a true coelom in the context of this question, as they are more accurately described as lacking any body cavity.

4. **Platyhelminthes**: This phylum includes flatworms, which are also acoelomates. They do not have a true coelom, but rather a solid body without a body cavity. However, they are not classified as pseudocoelomates.

### Conclusion
Based on the analysis:
- The correct answer is **Asclementis** (option 1), as it is the only phylum listed that does not possess a true coelom.

### Final Answer
The phylum that does not possess a true coelom is **Asclementis**.

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