Which of the following shows retrogressive metamorphosis?

Options

A. Sea squirt
B. Tongue worm
C. Lancelet
D. None of the above

Answer

**Step-by-Step Solution:**

1. **Understanding Retrogressive Metamorphosis**:
- Retrogressive metamorphosis is a process where the larval stage is more complex or advanced than the adult stage. This means that as the organism matures, it undergoes a significant reduction in complexity or structure.

2. **Identifying Examples**:
- The question asks for an example of an organism that exhibits retrogressive metamorphosis.

3. **Analyzing the Options**:
- The first option is Acidia (sea squids). In this case, the larval stage is highly mobile and complex, while the adult stage is stagnant and simpler in structure.
- The second option is Tongueworm (Balanoglossus). This organism does not exhibit retrogressive metamorphosis, as it has a partial notochord and does not show a reduction in complexity from larva to adult.
- The third option is Lancelet (Amphioxus). Similar to the Tongueworm, this organism does not show retrogressive metamorphosis, as it maintains a relatively simple structure throughout its life stages.

4. **Conclusion**:
- Based on the analysis, the only organism that shows retrogressive metamorphosis is Acidia (sea squids). Therefore, the correct answer is Acidia.

**Final Answer**: Acidia (sea squids) shows retrogressive metamorphosis.

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