A speciality of echinoderms is presence of

Options

A. Both epidermal exoskeleton and mesodermal endoskeleton
B. Ciliated epidermis
C. Coelom
D. None of the above.

Answer

**Step-by-Step Solution:**

1. **Understanding Echinoderms**: Echinoderms are a unique group of marine animals that include starfish, sea urchins, and sea cucumbers. They are characterized by their radial symmetry and a water vascular system.

2. **Identifying Special Features**: One of the most distinctive features of echinoderms is their skeletal structure. They possess both an epidermal exoskeleton and a mesodermal endoskeleton.

3. **Epidermal Exoskeleton**: The outer layer of echinoderms is covered by a hard exoskeleton made up of calcareous plates. This exoskeleton is derived from the epidermis, which is the outermost layer of cells.

4. **Mesodermal Endoskeleton**: Beneath the epidermis, echinoderms also have an endoskeleton made of calcareous ossicles, which are small structures that provide support and protection. This endoskeleton is derived from mesodermal tissue, which is the middle layer of cells in embryonic development.

5. **Comparison with Other Phyla**: Unlike echinoderms, other animal phyla may have exoskeletons or endoskeletons that are not specifically of epidermal or mesodermal origin. For example, arthropods have an exoskeleton made of chitin, which is different from the calcareous structure of echinoderms.

6. **Conclusion**: Therefore, the specialty of echinoderms lies in the presence of both an epidermal exoskeleton and a mesodermal endoskeleton, which is a unique characteristic that distinguishes them from other animal phyla.

**Final Answer**: The specialty of echinoderms is the presence of both an epidermal exoskeleton and a mesodermal endoskeleton.

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