Identify a deuterostome

Options

A. Leucosolenia
B. Dentalium
C. Dugesia
D. Ophiothrix.

Answer

To identify a deuterostome from the given options, we need to understand what a deuterostome is and how it differs from a protostome. Here’s a step-by-step solution:

### Step-by-Step Solution:

1. **Understand the Definition of Deuterostomes**:
- Deuterostomes are organisms in which the blastopore (the first opening that forms during embryonic development) develops into the anus. This is a key characteristic that distinguishes them from protostomes, where the blastopore develops into the mouth.

2. **Analyze the Given Options**:
- The options provided are:
- A) Leukosilenia
- B) Dentalium
- C) Dugesia
- D) Ophiothrix

3. **Evaluate Each Option**:
- **Leukosilenia**: This organism belongs to the phylum Porifera (sponges). Sponges do not have a true digestive system, and thus they do not form a mouth or anus in the traditional sense. Therefore, it is not a deuterostome.
- **Dentalium**: This organism is a mollusk, which belongs to the phylum Mollusca. Mollusks are protostomes, meaning their blastopore develops into the mouth first. Hence, it is not a deuterostome.
- **Dugesia**: This is a type of flatworm that falls under the phylum Platyhelminthes. Flatworms are also protostomes, as their blastopore develops into the mouth. Thus, it is not a deuterostome.
- **Ophiothrix**: This organism is a type of echinoderm, which belongs to the phylum Echinodermata. Echinoderms are deuterostomes, as their blastopore develops into the anus first.

4. **Conclusion**:
- Based on the analysis, the correct answer is **D) Ophiothrix**, as it is the only organism in the list that is a deuterostome.

### Final Answer:
**D) Ophiothrix**