A triploblastic animal with bilateral symmetry in lerval stage but asymmetry in adult is

Options

A. Arachnid
B. Echinoderm
C. Gastropod
D. Bivalve

Answer

To solve the question "A triploblastic animal with bilateral symmetry in larval stage but asymmetry in adult is," we will follow these steps:

### Step 1: Understand the Key Terms
- **Triploblastic**: This means the organism has three germ layers: ectoderm, mesoderm, and endoderm.
- **Bilateral Symmetry**: This means the organism can be divided into two equal halves along one axis.
- **Asymmetry**: This means that no matter how you cut the organism, you cannot get two equal halves.

### Step 2: Analyze the Options
1. **Arachnid**:
- Example: Spider or scorpion.
- Adult form is bilaterally symmetrical, so this option is incorrect.

2. **Echinoderm**:
- Example: Starfish.
- Adults exhibit radial symmetry, not asymmetry, so this option is also incorrect.

3. **Gastropod**:
- Example: Snail or conch (shank).
- Larvae are bilaterally symmetrical, but as they develop, they undergo torsion, resulting in asymmetry in the adult form. This matches the question's criteria.

4. **Bivalve**:
- Example: Pearl oyster.
- Bivalves have two shells and are bilaterally symmetrical in their adult form, making this option incorrect.

### Step 3: Conclusion
The only option that fits the description of having bilateral symmetry in the larval stage and asymmetry in the adult stage is **Gastropod**. Therefore, the correct answer is:

**Option 3: Gastropod**

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