Which of the following is correct about host-specific parasites?

Options

A. Such parasites can parasitise only a single species of host .
B. Both host and parasite tend to co-evolve
C. If host evolves special mechanisms for rejecting the parasite, the parasite has to evolve mechanism counteract and neutralize them to succeed with the host species,
D. All

Answer

To answer the question regarding host-specific parasites, we will analyze the characteristics of these parasites step by step.

### Step-by-Step Solution:

1. **Definition of Host-Specific Parasites**:
Host-specific parasites are those that can only infect a limited range of host species. They are not generalists and typically have a narrow host range.

**Hint**: Think about how some parasites are specialized for certain hosts rather than being able to infect many different types.

2. **Impact on Host**:
These parasites usually harm the host organism. The relationship is often detrimental to the host, leading to various health issues or even death.

**Hint**: Consider the nature of parasitism, which involves one organism benefiting at the expense of another.

3. **Co-evolution**:
Host-specific parasites and their hosts often engage in co-evolution. This means that as the host evolves defenses against the parasite, the parasite may also evolve mechanisms to overcome these defenses.

**Hint**: Reflect on the evolutionary arms race where both species adapt in response to each other.

4. **Host Mechanisms**:
Hosts may develop specific mechanisms to reject or combat the effects of the parasite. This can include immune responses or behavioral changes.

**Hint**: Think about how organisms adapt to survive threats in their environment.

5. **Conclusion**:
Based on the analysis, the correct statements about host-specific parasites include:
- They can parasitize only a single species of host.
- Both host and parasite tend to co-evolve.
- Hosts evolve mechanisms to reject parasites, and parasites evolve countermeasures.

Therefore, the correct answer is that all the provided statements about host-specific parasites are accurate.

### Final Answer:
All the statements regarding host-specific parasites are correct.