Ostium and osculum are sorrounded by

Options

A. choanocytes
B. myocytes
C. pinacocytes
D. spicules

Answer

**Step-by-Step Solution:**

1. **Understanding Ostium and Osculum:**
- Ostium (plural: ostia) refers to the small pores present all over the body of sponges. They allow water, along with nutrients, to flow into the sponge.
- Osculum is the larger opening through which water exits the sponge after passing through the body. It serves as an excretory structure.

2. **Identifying Surrounding Structures:**
- The question asks what surrounds the ostium and osculum. We need to identify the type of cells or structures that are associated with these openings in sponges.

3. **Analyzing the Options:**
- **Planocytes:** These are not related to the ostium and osculum. They are associated with the inner layer of sponges.
- **Myocytes:** These are contractile cells that help in the opening and closing of the ostia and oscula. They are responsible for regulating water flow.
- **Pinnacocytes:** These cells form the outermost layer of the sponge and do not surround the ostium and osculum.
- **Spicules:** These are structural elements that form the endoskeleton of sponges and do not surround the ostium and osculum.

4. **Conclusion:**
- The correct answer is **Myocytes** (Option B), as they are the cells that surround the ostium and osculum and are responsible for their function.