As you can observe, these phytoplankton possess a hard but flexible shell called the theca or lorica which is made of cellulose plates and extensions called horns, which are pretty pointy. This armour is divided in two by a horizontal groove called the cingulum. There’s also another small vertical groove crossing the cingulum which is called the sulcus. Each of these grooves are housing a flagellum which is used for locomotion during the motile stage of this eukaryotic unicellular algae.

Ceratium tends to bloom during summer and can be responsible for bad smell and taste of drinking water. They usually grow steadily during March and April and then their number explodes during June and July with exponential growth.