Raphidiopsis raciborskii is a cylindrical cyanobacterium found in freshwater environments worldwide. It ranges in size from 3 to 6 micrometers in width and 10 to 30 micrometers in length, often forming short filaments or trichomes. Each cell has a thick cell wall, contains chlorophyll-a and other pigments for photosynthesis, and possesses gas vesicles for buoyancy regulation. Raphidiopsis raciborskii can form dense blooms and produce toxins such as cylindrospermopsin and saxitoxins, posing risks to aquatic organisms and human health.