Protozoan motility — which of the following is NOT a locomotory mechanism used by protozoa? (Choose the exception and think of classic groups: flagellates, ciliates, amoebae.)

Introduction:
Protozoa are single-celled eukaryotic organisms that commonly move using specialized structures. Understanding true locomotory mechanisms helps distinguish protozoa from bacteria, algae, and slime molds.

Given Data / Assumptions:

• Candidate mechanisms: flagella, cilia, pseudopodia, gliding by slime secretion.
• We are asked to pick the option that is not used by protozoa.

Concept / Approach:
Most protozoa move via: (1) flagella in flagellates, (2) cilia in ciliates, or (3) pseudopodia in amoebae. Some apicomplexans have gliding motility, but it is substrate-dependent actomyosin-based propulsion and does not involve slime-trail secretion as seen in certain bacteria or slime molds.

Step-by-Step Solution:

Verification / Alternative check:
Flagellates (e.g., Giardia), ciliates (e.g., Paramecium), and amoebae (e.g., Amoeba proteus) are textbook examples. None rely on external slime-secretion for movement.

Why Other Options Are Wrong:

• Flagella: canonical in mastigophorans.
• Cilia: hallmark of ciliates.
• Pseudopodia: characteristic of amoebae.

Common Pitfalls:
Confusing apicomplexan “gliding motility” with slime-secretion gliding; apicomplexans do not lay a mucous trail like bacteria/slime molds.

Final Answer:
Gliding by slime secretion