What are functions of buccal cirri and wheel organ in amphioxus?

The buccal cirri and wheel organ in amphioxus serve different functions:

1. Buccal Cirri: These are finger-like projections located around the mouth of the amphioxus. They have several functions, including:

- Sensory perception: The buccal cirri are highly sensitive to touch and help the amphioxus detect and respond to changes in its environment.

- Feeding: The cirri help in capturing and manipulating food particles. They create water currents that bring in small organisms and particles, which are then trapped and directed towards the mouth for ingestion.

- Defense: The cirri can also be used for defense purposes. When threatened, the amphioxus can retract its cirri to protect its mouth and prevent potential predators from entering.

2. Wheel Organ: The wheel organ is a specialized structure located on the ventral side of the amphioxus, just behind the mouth. It is composed of cilia (hair-like structures) arranged in a circular pattern. The wheel organ functions in:

- Locomotion: The coordinated beating of the cilia in the wheel organ creates a rotating motion, allowing the amphioxus to move through the water. This movement helps the animal to swim and maintain its position in the water column.

- Filter feeding: The wheel organ also aids in filter feeding. The rotating cilia create water currents that bring in food particles, which are then trapped in mucus secreted by the wheel organ. The trapped particles are then transported towards the mouth for ingestion.

Overall, both the buccal cirri and wheel organ play important roles in the feeding, sensory perception, and locomotion of amphioxus.