Field of Science

Birth of a lichen

Lichens are symbiotic organisms consisting of a highly organized fungal mycelium enclosing algal cells. What's strange about lichens is that without the algae, the fungus just looks like a fungus. Without the fungus, the algae is just algae. They only take on the form recognized as a lichen when the two organisms are in that symbiotic association, and of course, the term itself means "living together". This presents some interesting aspects of reproduction. This illustration is from the November 2014 issue of the American Journal of Botany.  The sexual reproduction of the lichen is fungal in nature, so to form a new lichen, the fungus must capture a compatible algal cell anew.  This illustration shows this very early stage where fungal hyphae (filaments) have found and encircled an algae cell. The proliferation of the hyphae and the division of the algal cell is a demonstration that the symbiotic interaction, the lichenization, has begun. The accompanying article by William Sanders provides illustrated diagrams of the sexual and asexual reproductive cycles of lichens, all very nicely done.

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