Which of the following has stringing capsule or nematocytes ?

Options

A. Aurelia
B. Taenia
C. Pleurobrachia
D. Ascaris

Answer

To solve the question "Which of the following has stinging capsules or nematocytes?", we will analyze each option provided.

### Step-by-Step Solution:

1. **Understanding Nematocytes**:
- Nematocytes are specialized cells found in certain animals, particularly in the phylum Cnidaria. These cells contain stinging structures called nematocysts, which are used for defense and capturing prey.

2. **Analyzing Option 1: Aurelia**:
- Aurelia, commonly known as the moon jellyfish, belongs to the phylum Cnidaria.
- It has a mouth (manubrium) and its oral arms are equipped with stinging capsules (nematocytes).
- **Conclusion**: This option is correct.

3. **Analyzing Option 2: Tenia**:
- Tenia refers to tapeworms, which belong to the phylum Platyhelminthes.
- Tapeworms do not possess nematocytes or stinging capsules; they have hooks and suckers for attachment.
- **Conclusion**: This option is incorrect.

4. **Analyzing Option 3: Pleurobrachia**:
- Pleurobrachia, also known as comb jellies, belong to the phylum Ctenophora.
- While they have a gelatinous body and tentacles, they do not have nematocytes; instead, they use colloblasts for capturing prey.
- **Conclusion**: This option is incorrect.

5. **Analyzing Option 4: Ascaris**:
- Ascaris is a genus of parasitic roundworms (phylum Nematoda).
- They do not have nematocytes or stinging capsules; they have a different structure and mode of life.
- **Conclusion**: This option is incorrect.

### Final Answer:
The only organism among the options that has stinging capsules or nematocytes is **Aurelia**.