When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate. It is an example of

Options

A. Co-extinction
B. Alien species invasion
C. Over-exploitation
D. Habitat loss

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question states that when a host fish species becomes extinct, its unique assemblage of parasites also becomes extinct. We need to identify the ecological phenomenon that describes this relationship.

2. **Analyzing the Options**: The options provided are:
- A) Co-extinction
- B) Alien species invasion
- C) Over-exploitation
- D) Habitat loss

3. **Defining Co-extinction**: Co-extinction is a phenomenon where the extinction of one species leads to the extinction of another species that is dependent on it. In this case, the parasites are dependent on the host fish species for survival.

4. **Evaluating Other Options**:
- **Alien Species Invasion**: This refers to the introduction of non-native species that can disrupt local ecosystems. This does not relate to the extinction of a host and its parasites.
- **Over-exploitation**: This involves harvesting species at unsustainable rates, which does not directly relate to the extinction of a host and its associated parasites.
- **Habitat Loss**: This refers to the destruction of natural habitats, making them unable to support native species. While it can lead to extinctions, it does not specifically describe the relationship between a host and its parasites.

5. **Conclusion**: Since the extinction of the host fish species directly leads to the extinction of its unique assemblage of parasites, the correct answer is **A) Co-extinction**.

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