In sharks, one of the following is absent

Options

A. Claspers
B. Placoid scales
C. Cartilaginous endoskeleton
D. Air bladder

Answer

To answer the question "In sharks, one of the following is absent," we will analyze each option provided:

1. **Claspers**: Claspers are reproductive organs found in male sharks. They are used during mating for copulation. Therefore, claspers are present in sharks.

2. **Placoid Scales**: Sharks possess placoid scales, which are small, tooth-like structures that cover their skin. These scales are a characteristic feature of sharks and are modified teeth. Thus, placoid scales are present in sharks.

3. **Cartilaginous Endoskeleton**: Sharks belong to the class Chondrichthyes, which means they have a skeleton made of cartilage instead of bone. This cartilaginous endoskeleton is a defining feature of sharks. Therefore, the cartilaginous endoskeleton is present in sharks.

4. **Aeo Bladders**: Aeo bladders, or swim bladders, are gas-filled organs that help bony fishes maintain buoyancy. Sharks do not have swim bladders; instead, they rely on their large livers filled with oil for buoyancy and must swim continuously to avoid sinking. Therefore, aeo bladders are absent in sharks.

Based on the analysis above, the correct answer is:

**The aeo bladder is absent in sharks.**

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