In adult urochordate, lateral line system is absent because
(a) They are predator
(b) They have ampullae of Lorenzini
(c) They are sedentary
(d) They show progressive metamorphosis

Options

A. They are predator
B. They have ampullae of Lorenzini
C. They are sedentary
D. They show progressive metamorphosis Retrogressive metamorphosis is the feature of

Answer

To solve the question regarding the absence of the lateral line system in adult urochordates, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Urochordates**:
- Urochordates, also known as tunicates, are marine animals that exhibit a unique life cycle. In their adult form, they are typically sessile (attached to a substrate).

2. **Defining the Lateral Line System**:
- The lateral line system is a sensory organ found in many aquatic animals, primarily used to detect movement and vibrations in the water. This system is crucial for predatory and prey species to navigate and avoid threats.

3. **Analyzing the Options**:
- **Option (a)**: They are predators.
- This is incorrect because adult urochordates are not predators; they are filter feeders.
- **Option (b)**: They have ampullae of Lorenzini.
- This is also incorrect. Ampullae of Lorenzini are sensory organs found in some fish, not in urochordates.
- **Option (c)**: They are sedentary.
- This is correct. Adult urochordates are fixed to a substrate and do not require a lateral line system for detecting movement.
- **Option (d)**: They show progressive metamorphosis.
- While urochordates do undergo metamorphosis, this does not explain the absence of the lateral line system in adults.

4. **Conclusion**:
- The correct answer is **(c) They are sedentary**. Since adult urochordates are fixed in one place and do not need to detect movement in their environment, the lateral line system is not necessary.