Dimorphic protozoans are protozoans that have two distinct forms during their life cycle. They alternate between a motile form and a non-motile form. One example of a dimorphic protozoan is Polystomella.

Polystomella is a marine protozoan that belongs to the Foraminifera group. It has a benthic form that is attached to the sea floor and a planktonic form that is free-swimming. The benthic form is characterized by a calcareous shell that is made up of several chambers. The chambers are interconnected by small openings called foramina. The planktonic form, on the other hand, lacks a shell and has a single flagellum that it uses for swimming.

Polystomella undergoes alternation of generations during its life cycle. The benthic form reproduces asexually by budding to form small daughter cells. These daughter cells then grow and develop into the planktonic form. The planktonic form reproduces sexually to produce gametes that fuse to form a zygote. The zygote then develops into the benthic form.

In conclusion, Polystomella is an example of a dimorphic protozoan that alternates between a benthic form and a planktonic form during its life cycle. The benthic form reproduces asexually to produce daughter cells that develop into the planktonic form. The planktonic form reproduces sexually to produce a zygote that develops into the benthic form.

Polystomella