Britannica Sources used in this answer

How do protozoans use secreted coverings and shells for protection?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A pangolin walks through grass with a blue circle around it and the word endangered written in white across the image. — Integument The pangolin is the only mammal in the world covered in scales.

Protozoans utilize various secreted coverings and shells as part of their integument to protect themselves from environmental stressors and predation. These protective structures range from soft coatings to rigid, complex shells.12

Protective Structures

Tests: A test is a loose-fitting, protective shell secreted by organisms such as foraminiferans and radiolarians. These may be composed of substances secreted by the protozoan, such as calcium carbonate or silica, or they may incorporate foreign materials like sand grains and shell fragments for reinforcement.31
Loricae: Some protozoans secrete a lorica, a tubular or vaselike case. Like tests, these structures often incorporate external particles to enhance their protective properties.4
Cysts: Many protozoans secrete a protective cyst to survive unfavorable conditions, such as extreme temperatures, pollution, or lack of food. This dormant stage allows the organism to remain protected against environmental extremes for extended periods.5

These coverings serve as a vital barrier, separating the organism from its environment while allowing for necessary communication and interaction with the outside world.2