Teleost fish is differentiated externally from elasmobranch fish by

Options

A. Endoskeleton
B. Exoskeleton
C. Operculum
D. Stream line body

Answer

To differentiate teleost fish from elasmobranch fish externally, we can analyze the given options step by step:

1. **Understanding the Types of Fish**:
- Teleost fish belong to the class Osteichthyes, which are bony fish.
- Elasmobranch fish belong to the class Chondrichthyes, which are cartilaginous fish.

**Hint**: Remember the classification of fish based on their skeletal structure.

2. **Analyzing the Options**:
- **Endoskeleton**: This refers to the internal skeleton. Since it is not visible externally, this cannot be a distinguishing feature.

**Hint**: Think about where the endoskeleton is located and its visibility.

- **Exoskeleton**: Fish do not have an exoskeleton; instead, they have dermal scales. Therefore, this option is also incorrect.

**Hint**: Consider the type of protective covering fish have.

- **Operculum**: This is a bony flap that covers the gills in bony fish. Teleost fish have an operculum, while elasmobranchs do not. This is a significant external difference.

**Hint**: Recall the function of the operculum and its presence in different fish types.

- **Streamline Body**: Both teleost and elasmobranch fish have a streamlined body shape, which aids in swimming. Thus, this option does not differentiate them.

**Hint**: Compare the body shapes of both types of fish.

3. **Conclusion**:
- The correct answer is **Operculum** (Option C) because it is present in teleost fish and absent in elasmobranch fish, making it a key external differentiator.

**Final Answer**: Teleost fish is differentiated externally from elasmobranch fish by the presence of an operculum.

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