Definition
Peridinium is a genus of dinoflagellates, single-celled algae common in both marine and freshwater habitats. They possess armored cellulose plates called theca, giving them a distinctive appearance. They use two flagella for movement, creating a spinning motion. Most are photosynthetic, playing a vital role as primary producers. Some species can form harmful algal blooms. They're like the armored cars of the micro-world.