Which one is bioluminescent?

Options

A. Aurelia
B. Astraea
C. Adamsia
D. Metridium.

Answer

To solve the question "Which one is bioluminescent?" we will analyze the options provided and determine which organism has the ability to produce and emit light.

### Step-by-Step Solution:

1. **Understand Bioluminescence**:
- Bioluminescence is the ability of living organisms to produce and emit light. This occurs through a chemical reaction that converts chemical energy into light energy.

2. **Review the Options**:
- The options given are:
- A) Aurelia
- B) Astrea
- C) Adamsia
- D) Metridium

3. **Analyze Each Option**:
- **Aurelia**:
- Aurelia is a type of jellyfish that belongs to the phylum Cnidaria. Jellyfish are known for their bioluminescent properties. Thus, Aurelia is bioluminescent.
- **Astrea**:
- Astrea refers to sea snails, which belong to the phylum Mollusca. Sea snails do not exhibit bioluminescence. Therefore, this option is incorrect.
- **Adamsia**:
- Adamsia, also known as sea anemone, is another member of the phylum Cnidaria. However, sea anemones do not have the ability to produce light. Thus, this option is also incorrect.
- **Metridium**:
- Metridium, known as the plumose anemone, is again a member of the phylum Cnidaria. Similar to Adamsia, Metridium does not exhibit bioluminescence. Therefore, this option is incorrect as well.

4. **Conclusion**:
- After analyzing all the options, the only organism that is bioluminescent is **Aurelia** (the jellyfish).

### Final Answer:
**Aurelia** is the bioluminescent organism among the options provided.

---