Which of the following has statocyst as balancing organ ?

Options

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

Answer

To solve the question "Which of the following has statocyst as a balancing organ?" we will analyze each option provided and determine which organism possesses a statocyst.

### Step-by-Step Solution:

1. **Understanding Statocyst**:
- A statocyst is a sensory organ that helps in maintaining balance and equilibrium in certain aquatic invertebrates. It typically contains sensory hair-like structures called cilia that respond to gravity and movement.

2. **Analyzing the Options**:
- **Option A: Aurelia**
- Aurelia is commonly known as jellyfish. Jellyfish do not possess statocysts; instead, they have other mechanisms for balance. Therefore, this option is incorrect.

- **Option B: Taenia**
- Taenia is known as a tapeworm. Tapeworms are flatworms and do not have statocysts. They lack a complex nervous system that would include such balancing organs. Thus, this option is also incorrect.

- **Option C: Pleurobrachia**
- Pleurobrachia is a genus of ctenophores (comb jellies). Ctenophores are known to have statocysts, which are used for balance and orientation in the water. This makes Pleurobrachia a strong candidate for the correct answer.

- **Option D: Ascaris**
- Ascaris is a genus of parasitic roundworms. They do not have statocysts as they do not require such balancing organs due to their lifestyle. Therefore, this option is incorrect.

3. **Conclusion**:
- After analyzing all the options, the only organism that has a statocyst as a balancing organ is **Pleurobrachia**.

### Final Answer:
**Pleurobrachia** has statocyst as a balancing organ.

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