Internal endoskeleton of starfish is made up of calcareous plates called ossicles. Ossicles are derived from

Options

A. ectoderm
B. mesoderm
C. endoderm
D. both 1) and 3)

Answer

To determine the origin of ossicles, the calcareous plates that form the internal endoskeleton of starfish, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of Starfish**:
- Starfish belong to the phylum Echinodermata, which is characterized by their unique body structure, including an internal endoskeleton made of calcareous plates known as ossicles.

2. **Identify the Function of Ossicles**:
- Ossicles serve important functions such as providing rigidity and protection to the starfish's body. They are embedded in the dermis of the body wall and are immovable.

3. **Know the Germ Layers**:
- In embryonic development, organisms typically have three primary germ layers: ectoderm, mesoderm, and endoderm. Each layer gives rise to different tissues and structures in the body.

4. **Determine the Origin of Ossicles**:
- In echinoderms like starfish, ossicles are derived from the mesoderm. This is the layer responsible for forming structures such as bones, muscles, and the internal skeleton.

5. **Select the Correct Option**:
- Given the options: ectoderm, mesoderm, endoderm, and both 1 and 3, the correct answer is mesoderm (Option B).

### Final Answer:
The ossicles of starfish are derived from the **mesoderm**.

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