ants or termites have eaten a big meal of wood or leaves, they eat some fungus from their
gardens. The fungus helps them digest thecellulosein the wood or leaves. The two species
are actually dependent on each other for survival. Ambrosia beetles live in the bark of trees.
Like ants and termites, they grow fungi inside the bark of trees where they live and use it
to help digest their food.
Fungi as Parasites
Althoughlotsofsymbioticrelationshipshelpbothorganisms, sometimesoneoftheorganisms
is harmed. When that happens, the organism that benefits and is not harmed is called a
parasite. Have you ever heard of Dutch elm disease? In the late 1960s elm trees in the
United States began to die. Since then much of the species has been eliminated. The disease
was caused by a fungus that acted as a parasite. The fungus that killed the trees was carried
by beetles that inoculated the tree with the fungus. The tree tried to stop the growth of the
fungus by blocking its own ability to gain water. However, without water the tree soon dies.
Some parasitic fungi cause human diseases such as athlete’s foot and ringworm. These fungi
feed on the outer layer of warm, moist skin.
Fungi as Predators
It might seem that fungi growing on a tree trunk or a mushroom in your yard are passive and
participating in very little activity, but did you know that some fungi are actually hunters?
Some fungi trap nematodes. A nematode is a kind of a worm and is often dinner to fungi.
These hungry fungi live deep in the soil where they set traps for unsuspecting nematodes
by making a circle with theirhyphae.Hyphae are sort of the ”arms and legs” of a fungus;
they look like cobwebs and can be sticky. Fungi set out circular rings of hyphae with a lure
inside which brings the nematode inside the fungus (Figure9.10).
Fungi are Good Eaters
Fungi can grow fast because they are such good eaters. Fungi have lots of surface area
and this large surface area “eats.” Surface area is how much exposed area an organism has
compared to their overall volume, and in the mushroom for example, most of that surface
area is actually underground. They also have special enzymes that they can squirt into their
environment which helps them digest large organic molecules. Sort of like how you might
cut up your meat or vegetables before eating, fungi “cut up” large molecules such as sugars,
proteins, and lipids into smaller molecules. Then the fungi absorb the nutrients into their
cells.