Fig. 3

Microscopic documentation of the degradation of chloroplasts. Differential interference (left) and fluorescent images (excitation: 400–440 nm) (right). a Cell of heterotrophic euglenid Peranema trichophorum (center) containing phagosomes of variable color, which is surrounded by live cells of the green alga Chlorogonium capillatum (arrows). Among the ingesta, the autofluorescence intensity differs more than the color, indicating the progress of chlorophyll catabolism together with chloroplast digestion (arrowheads); b cell of the heterotrophic heliozoan (Haptista) Choanocystis sp. that had ingested C. capillatum, demonstrating that chlorophyll autofluorescence gradually disappeared in an early stage of digestion (arrowheads); c cells of Euglena gracilis in an aged culture, showing the formation of brown granules after chloroplast dismantling, where the loss of chlorophyll autofluorescence was observed in the earliest stage. Cells of d the chlorarachniophyte Chlorarachnion reptans; and e the haptophyte Calyptrosphaera sphaeroidea, respectively, both showing the formation of nonfluorescent reddish-brown granules (arrowheads); f cells of Palpitomonas bilix that had ingested a pedinophycean green alga, demonstrating that the pigmentation of the dietary alga was also lost within the phagosome (arrow: in the earliest stage of digestion; arrowheads: in the later stages), in contrast to the CPE-producing algivores