Osteichthyes can be differentiated from chondrichthyes externally by the presence of:-

Options

A. Ventral mouth
B. Lateral line sensory system
C. Terminal mouth
D. Clasper

Answer

To differentiate Osteichthyes (bony fishes) from Chondrichthyes (cartilaginous fishes) externally, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Groups**:
- Osteichthyes refers to bony fishes, which have a skeleton made of bone.
- Chondrichthyes refers to cartilaginous fishes, which have a skeleton made of cartilage.

2. **Identifying External Features**:
- We need to focus on external features that can help us differentiate between these two groups.

3. **Analyzing the Options**:
- **Option 1: Ventral Mouth**: This feature is more characteristic of Chondrichthyes, not Osteichthyes.
- **Option 2: Lateral Line Sensory System**: Both groups possess this system, so it does not serve as a distinguishing feature.
- **Option 3: Claspers**: Claspers are found in Chondrichthyes, specifically in males for reproduction, and are not present in Osteichthyes.
- **Option 4: Presence of a Swim Bladder**: Osteichthyes typically have a swim bladder, which aids in buoyancy, whereas Chondrichthyes do not.

4. **Conclusion**:
- The correct distinguishing feature that differentiates Osteichthyes from Chondrichthyes externally is the **presence of a swim bladder**.

### Final Answer:
Osteichthyes can be differentiated from Chondrichthyes externally by the presence of a **swim bladder**.

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