P. dubius feeds on a range of filamentous cyanbacteria using its cytopharyngeal basket - a specialised oral structure for prey capture and ingestion.
Digestion is a two-stage process:
- Very rapid destruction of the cell walls of the cyanobacterium. This occurs within a matter of seconds and enables the ciliate to ingest large quantities of cyanobacterial filaments in a short time.
- The initially single, very voluminous food vacuole becomes reduced to numerous small vesicles 1–2µm in diameter. The following digestion of the cyanobacterial protoplasts takes several hours (Peck and Hausmann, 1980).