What are cysts in protozoa known for?

Cysts in protozoa are known primarily for being the infectious form that is resistant to environmental stresses, including chlorine. This resistance allows them to survive in adverse conditions that would typically be lethal to other forms of life, such as exposure to disinfectants used in water treatment. Cysts can remain viable for extended periods, making them potentially infectious when ingested by hosts or when they contaminate water supplies.

The cyst form serves as a protective capsule, allowing protozoa to endure harsh environmental conditions, including extreme temperatures and desiccation. This characteristic is particularly significant in waterborne protozoan pathogens, where cysts can be distributed in contaminated water and pose health risks to humans and animals.

In contrast to the role of cysts as infectious agents, other forms of protozoa, such as trophozoites, are actively replicating and metabolizing, but are typically more susceptible to disinfection processes. Choosing the correct answer highlights the crucial role cysts play in the transmission and survival of protozoan parasites in the environment.