Question

‘Wheel organ' is found in
A. Herdmania
B. Amphioxus
C. Balanoglossus
D. All of the above

Answer 1

Hint: They are fish-le benthic filter-feeding chordates.

Complete answer:
The wheel organ is the specialized epithelium in the roof and the sides of the adult amphioxus oral cavity. Amphioxus is also called a lancelet.
Wheel organ borders the oral epithelium properly. These cells are tall and strongly ciliated and have dark, heterochromatin-rich nuclei.

Additional information
- Amphioxus holds a wheel organ which is also known as the rotatory gland or muller’s gland in the vocal hood.
- It produces a whorling liquid flow to clean food bion into the mouth.
- It borders the oral epithelium proper, separated by a thin strip of margin cells which are not ciliated but contain a few large dense cored vesicles apically.
- The organ is further specialized, forming the so-called Hatschek's groove having two ciliated cell types.
- Each cell bears one tall cilium surrounded by microvilli and is involved in the production of secretory material into the groove.
- The task of the wheel organ is to transport dissolved particles towards the mouth. It draws food through the use of its cilia for digestion.

So, the correct answer is Amphioxus.

Note: The name amphioxus or lancelet is taken from Greek which refers to its shape as “both ends pointed “, they are cephalochordates which are small, eel-like, unprepossessing animals that spend much of their time buried in the sand.