At retrogressive metamorphosis the urochordate larva

Options

A. loses notochord
B. loses tail
C. experiences reduction of nervous system to a visceral ganglion
D. all the above

Answer

To solve the question regarding retrogressive metamorphosis in urochordate larvae, we can break it down into several steps:

### Step-by-Step Solution:

1. **Understanding Retrogressive Metamorphosis**:
- Retrogressive metamorphosis refers to the process where an organism transforms from a more complex larval stage to a simpler adult form. This means that the larva has more advanced features compared to the adult.

2. **Characteristics of Urochordate Larvae**:
- Urochordate larvae possess several features that are characteristic of chordates, including a structure called the notochord, a tail, and a well-developed nervous system.

3. **Analyzing the Options**:
- **Option 1: Loses Notochord**: In urochordate larvae, the notochord is present in the tail region. During metamorphosis, this structure is lost in the adult form.
- **Option 2: Loses Tail**: The tail is essential for swimming in the larval stage, but it is absent in the adult form, indicating a loss of this feature.
- **Option 3: Experiences Reduction of the Nervous System to a Visceral Ganglion**: The larval stage has a well-developed central nervous system, which is simplified to a visceral ganglion in the adult form.

4. **Conclusion**:
- Since all three statements (losing the notochord, losing the tail, and reduction of the nervous system) are true during retrogressive metamorphosis in urochordates, the correct answer is **Option 4: All of the above**.

### Final Answer:
The correct answer is **Option 4: All of the above**.

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