The simplest way for a filamentous fungus to reproduce asexually is by fragmentation: a mycelium fragments leading to new mycelia.
Yeast like Saccharomyces cerevisae reproduce by budding or budding. Sprouts (twins) usually separate from the parent but may eventually stick together, forming chains of cells.
In terrestrial fungi, fruiting bodies produce, by mitosis, abundant, light cells that are scattered throughout the medium. Each of these cells, a spore known as conidiospore (from the Greek, konis = dust), when dropped into an appropriate material, is capable of generating a new mold, mold, etc.
For the production of this kind of spore the tip of a hypha protrudes from the substrate and suddenly produces hundreds of conidiospores, which remain united until released. that's what happens with the fungus penicillium, which was named after the fact that the spore - producing structure - the conidia - resembles a brush.
Below - Scanning electron micrograph showing the fruiting body of the Penicillium sp. Frequent mold found in fruits. The small, light spherical spores (conidiospores) sprout from conidia that emerge at the end of a specialized hyphae, the conidiophore.
Orange contaminated with Penicillium sp, sight with the naked eye.
In certain aquatic fungi, spores are provided with flagella, an adaptation to dispersion in liquid medium. Because they are mobile and actively swimming, these spores are called zoospores.
In the reproductive cycle of some aquatic fungi, there is the production of flagellate gametes, which fuse and generate zygotes that will produce new individuals. In terrestrial fungi, there is a reproduction cycle in which meiosis spores are produced. Developing, these spores generate haploid hyphae that later fuse and generate new diploid hyphae, within which new meioses will occur for the production of more meiotic spores. The alternation of meiosis and fusion of hyphae (which behave like gametes) characterizes the process as sexual.
The scheme in the figure below illustrates a generic breeding cycle, valid for most fungi. Many alternate between sexual and asexual reproduction. In others, only sexual reproduction or only asexual reproduction may occur.
In general, the sexual reproduction of the fungi begins with the fusion of haploid hyphae, characterizing the plasmogamy (cytoplasmic fusion). Genetically different haploid nuclei from each parental hypha remain separate (heterocariotic phase, n + n).
Subsequently, nuclear fusion (karyogamy) generates diploid nuclei which, dividing by meiosis, produce haploid spores. Spores formed by meiosis are considered sexed (by the variety due to the meiotic process).
Some curiosities deserve to be mentioned about the sexual phase of reproduction:
- Before plasmogamy occurs, one hypha must "attract" the other. This occurs through the production of pheromones"sexually attracting" substances produced by compatible hyphae;
- in many fungi after plasmogamy it takes a long time (days, months, years) until cariogamy;
- The production of meiotic spores after the occurrence of karyogamy occurs in special structures, often called sporangia.