The valves often bear radially symmetrical ornamental patterns that can appear as dots when viewed with an optical microscope. Some also bear spines on their valves, which may either increase cell surface area and reduce sinking, or act as a deterrent to zooplankton grazers. Unlike pennate diatoms, centric diatoms never have a raphe.
Radially symmetrical ornamental patterns are commonly found on the valves of these organisms, appearing like dots under an optical microscope. Some valves also have spines that can either increase cell surface area and reduce sinking or act as a deterrent to zooplankton predators. Unlike pennate diatoms, centric diatoms never feature a raphe.