Zygomycota
Zygomycota, or zygote fungi, are a
division of
fungi. The name of the division comes from zygosporangia, resistant structures formed during
sexual reproduction. There are approximately 600 species of zygomycetes known. They are mostly terrestrial in habitat, living in soil or on decaying plant or animal material. A group of zygomycetes form
mycorrhizae, mutualistic associations with the roots of plants, and are of major importance. Zygomycete
hyphae are
coenocytic, with septa only where
gametes are formed.
A common example of a zygomycete is black bread mold (
Rhizopus stolonifer). It spreads over the surface of bread or other food sources, sending hyphae inward to absorb nutrients. In its
asexual phase it develops bulbous black
sporangia at the tips of upright hyphae, developing hundreds of haploid
spores inside that are dispersed into the air. If environmental conditions deteriorate and
mycelia of opposite mating types are present, the fungus reproduces sexually and produces zygosporangia. Zygosporangia are highly resilient to environmental hardships, and are metabolically inert. When conditions improve, however, they develop and release haploid spores.
Some zygomycetes disperse their spores in a more precise manner than simply allowing them to drift aimlessly on air currents.
Pilobolus, a fungus which grows on animal dung, bends its sporangium-bearing hyphae towards light and then "fires" them with an explosive squirt of high-pressure
cytoplasm. Sporangia can be launched as far as 2m, placing them far away from the dung and hopefully on vegetation which will be eaten by an herbivore, eventually to be deposited as dung elsewhere.
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