Question

Myonemes are the fine contractile structures in the pellicle and best developed in class___
A) Sarcodina
B) Ciliata
C) Sporozoa
D) All of the above

Answer 1

Hint: Pellicle provides protection to the cell membrane in many types of protozoa. It is like a blanket of protein for extra security to the unicellular organisms of the kingdom Protista under the class Protozoa.

Complete Answer:
What exactly is the pellicle? A pellicle is a very thin layer of protein that protects cell membranes in many types of protozoa, which are free-living or parasitic single-celled eukaryotes that feed on organic matter such as other microorganisms or organic tissues and debris.
The members of protozoa like Plasmodium, Paramecium, Leishmania, are heterotrophic. They either depend on the decomposing of the organic matter to obtain the nutrients or depend on the host cells, in which they cause the disease. The pellicle serves as an additional advantage to these single-celled organisms to thrive and function.

The pellicle, which is directly below the cell membrane and surrounds the cytoplasm, allows organisms like paramecia and ciliates to hold their shapes. The fine layers of translucent membranes also facilitate movement because it is flexible owing to its proteinaceous makeup. The contractile myonemes help in movement by contracting and relaxing.
Myonemes, as evident by their function that we have just discussed, as such protein filaments that can contract when exposed to the calcium ions.
The options provided to us are the classes of Protozoa (as shown below), therefore, all of these will have the myonemes present in the pellicle.

Therefore, the correct answer is option D.

Note: Most of the protozoans are either parasitic or saprophytic, therefore, the pellicle also plays an important role in protection.