Chytrids are parasitic fungi of eucaryotic algae and blue-green algae. Endocoenobium eudorinae sits within a coenobium of Eudorina elegans. At the left: The coenobium contains just two living algal cells. The fungus is hardly visible (photo taken with the help of a light microscope). At the right: the same detail as seen through a fluorescence microscope after dying with Calcufluor white. The dye stains solely the fungus. The two intact algal cells have not yet been found by the rhizoids of the fungus, all other (destroyed) cells are in direct contact.

Chytridium microcystides on Microcystis aeruginosa (Calcufluor white staining). At the left: the fungus develops claw-like structures at the endings of the rhizoids that help it to enclose a cell of a blue-green alga. At the right: heavy mycosis of a colony of blue-green algae. The algal cells can be recognized as grey spots due to the fluorescence of their chlorophyll.

Blastocladiella anabaenae on Anabaena flos-aquae. At the left: the rhizoid system of the fungus becomes visible due to the staining with Calcufluor white. At the right: degenerate filaments of blue-green algae (U. MÜLLER and P. v. SENGBUSCH, 1983).