The skeleton of bath sponge, Euspongia, is made of

Options

A. Spongin fibers
B. Siliceous spicules
C. Calcareous spicules
D. Spongin fibers and siliceous spicules

Answer

To determine the composition of the skeleton of the bath sponge, Euspongia, we can follow these steps:

### Step 1: Understand the Types of Sponges
Sponges are classified into different classes based on their skeletal structure. The main classes include Calcarea, Hexactinellida, and Demospongiae.

### Step 2: Identify the Skeleton Composition
- **Calcareous spicules**: These are made of calcium carbonate and are found in sponges of the class Calcarea.
- **Siliceous spicules**: These are made of silica and are present in sponges of the class Hexactinellida.
- **Spongin fibers**: These are a type of protein fiber found in the skeleton of sponges belonging to the class Demospongiae.

### Step 3: Classify Euspongia
Euspongia, commonly known as the bath sponge, belongs to the class Demospongiae.

### Step 4: Determine the Skeleton Composition of Euspongia
Since Euspongia is part of the Demospongiae class, its skeleton is primarily made up of spongin fibers.

### Conclusion
The skeleton of the bath sponge, Euspongia, is made of **spongin fibers**.

### Final Answer
The correct answer is **A) Spongin fibers**.

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