Green sun animalcule. Light microscope footage of a green sun animalcule, Acanthocystis sp. Acanthocystis is a genus of organisms known as heliozoans, microbial eukaryotic protists with stiff arms (axopodia) radiating from their spherical bodies. Some species, such as this one, are called green sun animalcules because their bodies are coloured by harmless symbiotic green algae (zoochlorellae). Heliozoans feed in the same way as amoebas, by engulfing their prey. Filmed with differential interference contrast illumination.