Question

Ciliated organ of Muller is
(a) Velum
(b) Wheel organ
(c) Branchial sac
(d) None of the above

Answer 1

Hint: This organ is found in the roof and sides of the oral cavity in lancelets as an epithelium. This organ is ciliated and borders the oral epithelium.

Complete answer:
The wheel organ is the ciliated organ of Muller and is known to be a specialized epithelium. Muller organ is usually a swelling that is formed by the accumulation of scolopophore. The wheel organ is generally separated by a thin strip of margin cells. These cells are not ciliated like the ones found in the wheel organ but have large and dense cored vesicles.
The wheel organ is usually long and contains ciliated cells. It also contains dark, heterochromatic rich nuclei. Muller's organ is usually found in arthropods and insects belonging to the Acrididae family.

Additional information:
Wheel organ undergoes specialization dorsally to form the Hatschek's groove. This groove contains two types of ciliated cells.
The first type of cell secretes a dense and granular material. The granules are stored and released through the cell membrane into the body cavities filled with blood.
The other type of cells found in Hatschek's groove is rod-shaped and contains apical cellular regions. Here each cell contains one tall cilium which is generally surrounded by microvilli. These cells are often involved in the production of secretory material in the groove.

So, the correct answer is ‘Wheel organ’.

Notes:
One of the main functions of the wheel organ is to transport dissolved particles towards the mouth. As the oral cavity consists of cilia food particles are drawn by them for digestion.