All of the following are related to Aplysia, except.

Options

A. Triploblastic
B. Eucoelomate
C. Bilaterally symmetrical
D. Water vascular system

Answer

To solve the question, we need to identify which of the provided options is not related to Aplysia. Let's break down the characteristics of Aplysia and the options given.

### Step-by-Step Solution:

1. **Understanding Aplysia**:
- Aplysia is a genus of sea slugs, specifically known as sea hares. They belong to the phylum Mollusca and the class Gastropoda.

2. **Analyzing the Options**:
- We need to evaluate each option to see if it relates to the characteristics of Aplysia or the phylum Mollusca.

3. **Option 1 - Triploblastic**:
- Members of the phylum Mollusca, including Aplysia, are triploblastic, meaning they have three germ layers (ectoderm, mesoderm, and endoderm).
- **Conclusion**: This option is correct.

4. **Option 2 - Eucoelomate**:
- Aplysia is eucoelomate, which means it has a true coelom (body cavity). This is a characteristic of the phylum Mollusca.
- **Conclusion**: This option is correct.

5. **Option 3 - Bilaterally Symmetrical**:
- Aplysia exhibits bilateral symmetry, meaning its body can be divided into two equal halves. This is also a characteristic of mollusks.
- **Conclusion**: This option is correct.

6. **Option 4 - Water Vascular System**:
- The water vascular system is a characteristic of the phylum Echinodermata (e.g., starfish, sea urchins) and is not found in mollusks like Aplysia.
- **Conclusion**: This option is incorrect regarding Aplysia.

### Final Answer:
- The option that is not related to Aplysia is the **water vascular system**.