Light micrograph of the ciliate Pseudomicrothorax dubius. Pseudomicrothorax devours cyanobacterial filaments, mainly of the genus Oscillatoria, within a short time. The ciliate belongs to the order Nassulida, the members of which possess a special mouth-feeder with which filamentous cyanobacteria are devoured. Microscopic contrast method : Differential interference contrast. Magnification 800x at a print width of 10 cm.