Infection of algae-free Climacostomum virens with symbiotic Chlorella sp. isolated from algae-containing C. virens.

The ciliate Climacostomum virens normally contains algae as symbionts in its cytoplasm and retains them over many generations. An aposymbiotic strain of C. virens which cannot re-establish a new symbiotic association by ingestion of algae derived from green Climacostomum was recently isolated in our laboratory.