Endosymbiosis

The endosymbiotic theory holds that the origin of all eukaryotes began when one prokaryote cell consumed another, but instead of being digested, they formed a mutualistic partnership. The consumed proteobacterium, what would become the mitochondria, gained shelter and access to nutrients in exchange for the aerobic respiration it would provide the host cell. Likewise in a second event with a cyanobacterium becoming the ancestral chloroplast, respectively trading photosynthesis. Therefore lichen, as a composite organism (algae within fungi), represents a macro-scale occurrence of the micro-scale endosymbiosis found within it's own cells.

The lichen’s algal photobiont is to the fungal mycobiont as the mitochondria/chloroplast is to the eukaryotic cell. The algae lives within the fungi in exchange for its photosynthetic products. Shelter for nutrients/energy, to the benefit of both parties.

The idea of this simple connection gave me one of those moments of fascination. On the small mirroring the large. With these independent events perhaps being driven by similar evolutionary pressures, but at different relative scales. One intracellular, the other at the tissue/organism level.

Focus stacked image of 93 photographs.

Image size 5454 x 3636 pixels.

Actual size 9mm wide x 6mm tall.