Black bread mold

The common black bread mold (Rhizopus stolonifer) is an example of a conjugating mold. It produces three types of hyphae:

stolon hyphae spread over the surface of bread as the mycelium grows,

rhizoid hyphae penetrate the bread to digest it and to anchor the mycelium, and

sporangiophores are upright hyphae that form a sporangium at their tips.

Asexual mitospores (spores formed by mitosis) within the sporangia are released when mature. Germination of these spores forms the haploid hyphae of a new mycelium.

Asexual reproduction by mitospores occurs continuously. Sexual reproduction occurs only when opposite mating types (designated + and -) come in contact. Then special cells become gametes that fuse forming a zygote. The zygote develops a resistant cell wall, forming a zygospore, the characteristic that gives its name to this group of fungi. Subsequently, the zygospore germinates and forms a sporangiophore whose sporangium produces both + and - haploid spores.