Similarity between adult Amphioxus and adult Petromyzon is

Options

A. Presence of 6-15 pairs of gill slits
B. Presence of paired fins
C. Presence of notochord
D. Presence of vertebrae

Answer

To determine the similarity between adult Amphioxus and adult Petromyzon, we can analyze the characteristics of both organisms step by step.

### Step-by-Step Solution:

1. **Identify the Organisms**:
- Amphioxus belongs to the subphylum Cephalochordata.
- Petromyzon (lamprey) belongs to the subphylum Vertebrata.

2. **Examine Their Classification**:
- Both Amphioxus and Petromyzon are part of the phylum Chordata.
- Chordata is divided into three subphyla: Urochordata (tunicates), Cephalochordata (Amphioxus), and Vertebrata (lampreys and other vertebrates).

3. **Look for Common Features**:
- Both organisms possess a notochord at some stage of their life cycle. However, in adults, the notochord is replaced by a vertebral column in vertebrates.
- Amphioxus retains a notochord throughout its life, while Petromyzon has a well-developed vertebral column.

4. **Analyze Specific Features**:
- **Gill Slits**: Adult Petromyzon has 6-15 pairs of gill slits, while Amphioxus also has gill slits but they are not as numerous.
- **Paired Fins**: Petromyzon has paired fins, but Amphioxus does not possess paired fins.
- **Vertebral Column**: The most significant similarity is that both organisms have a notochord in some form. However, only Petromyzon has a true vertebral column in adulthood.

5. **Conclusion**:
- The primary similarity between adult Amphioxus and adult Petromyzon is the presence of a notochord in Amphioxus and a vertebral column in Petromyzon, but the correct answer to the question regarding their similarity in adult form is the presence of a vertebral column in Petromyzon.

### Final Answer:
The similarity between adult Amphioxus and adult Petromyzon is the presence of a vertebral column in Petromyzon (Option D).

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