In which the following notochord is absent?

Options

A. Adult tunicate
B. Myxine
C. Amphioxus
D. Larval tunicates

Answer

To determine in which of the following options the notochord is absent, we will analyze each option provided.

### Step-by-Step Solution:

1. **Understand the Notochord**:
- The notochord is a flexible, rod-like structure that provides support in the embryonic stages of chordates. It is made of cartilage and is a key characteristic of the phylum Chordata.

2. **Identify the Options**:
- The options given are:
1. Adult Tunicate
2. Myxine
3. Amphioxus
4. Larval Tunicate

3. **Evaluate Each Option**:
- **Adult Tunicate**: In adult tunicates, the notochord is absent. Adult tunicates lose their notochord as they develop into their adult form.
- **Myxine**: Myxine (hagfish) possesses a notochord throughout its life, so this option is incorrect.
- **Amphioxus**: Amphioxus (lancelet) retains a notochord throughout its life, making this option also incorrect.
- **Larval Tunicate**: In larval tunicates, the notochord is present. Therefore, this option is incorrect as well.

4. **Conclusion**:
- The only option where the notochord is absent is the **Adult Tunicate**.

### Final Answer:
The notochord is absent in **Adult Tunicate**.

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