Light micrograph of the freshwater green alga Haematococcus pluvialis. Haematococcus forms pear-shaped cells suspended in a swollen cell wall. Two flagella move the cells forward. Haematococcus is mainly found in very small waters that dry out quickly. To protect themselves from UV radiation, the cells then form a red carotenoid, astaxanthin. The water eventually turns visibly blood-red. Culture material from the algae collection at the University of Cologne (CCAC). Microscopic contrast method : Differential interference contrast. Magnification 600x at a print width of 10 cm.