The anterior part of Amphioxus is

Options

A. Oral hood
B. Rostrum
C. Mouth
D. Both A and B

Answer

To answer the question regarding the anterior part of Amphioxus, we can break down the solution into several clear steps:

### Step-by-Step Solution:

1. **Understanding Amphioxus**:
- Amphioxus, also known as Branchiostoma, is a marine organism that belongs to the subphylum Cephalochordata. It is a type of lancelet, which is characterized by its elongated, fish-like shape.

2. **Identifying the Structure**:
- The body of Amphioxus has both anterior (front) and posterior (back) ends that are pointed. This pointed shape is a defining characteristic of lancelets.

3. **Locating the Anterior Part**:
- The anterior part of Amphioxus is specifically referred to as the "rostrum." The rostrum is the most forward point of the organism and plays a crucial role in its feeding mechanism.

4. **Function of the Rostrum**:
- The rostrum's pointed shape is advantageous for the organism as it helps in capturing prey. It allows Amphioxus to burrow into the sand and sift through sediment for food.

5. **Differentiating Other Structures**:
- While the oral hood and mouth are present in the anterior region, they are not the most anterior structures. The oral hood is an extension of the buccal cavity and is located ventrally (on the underside), and the mouth is also positioned at the level of the oral hood.

6. **Conclusion**:
- Therefore, the correct answer to the question "The anterior part of Amphioxus is" is **B) Rostrum**.