Fungi Asexual Reproduction

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 Micrograph shows budding yeast cells. The parent cells are stained dark blue and round, with smaller, teardrop shaped cells budding from them. The cells are about 2 microns across and 3 microns long.
Budding in Histoplasma. The dark cells in this bright field light micrograph are the pathogenic yeast Histoplasma capsulatum, seen against a backdrop of light blue tissue. Histoplasma primarily infects lungs but can spread to other tissues, causing histoplasmosis, a potentially fatal disease. (credit: modification of work by Dr. Libero Ajello, CDC; scale-bar data from Matt Russell)

OpenStax Biology 2e

Fungi reproduce asexually by fragmentation, budding, or producing spores. Fragments of hyphae can grow new colonies. Somatic cells in yeast form buds. During budding (an expanded type of cytokinesis), a bulge forms on the side of the cell, the nucleus divides mitotically, and the bud ultimately detaches itself from the mother cell.

The most common mode of asexual reproduction is through the formation of asexual spores, which are produced by a single individual thallus (through mitosis) and are genetically identical to the parent thallus. Spores allow fungi to expand their distribution and colonize new environments. They may be released from the parent thallus either outside or within a special reproductive sac called a sporangium.

The asexual and sexual stages of reproduction of fungi are shown. In the asexual life cycle, a haploid (1n) mycelium undergoes mitosis to form spores. Germination of the spores results in the formation of more mycelia. In the sexual life cycle, the mycelium undergoes plasmogamy, a process in which haploid cells fuse to form a heterokaryon (a cell with two or more haploid nuclei). This is called the heterokaryotic stage. The dikaryotic cells (cells with two more more nuclei) undergo karyogamy, a process in which the nuclei fuse to form a diploid (2n) zygote. The zygote undergoes meiosis to form haploid (1n) spores. Germination of the spores results in the formation of a multicellular mycelium.
Generalized fungal life cycle. Fungi may have both asexual and sexual stages of reproduction. Source: OpenStax Biology 2e

There are many types of asexual spores. Conidiospores are unicellular or multicellular spores that are released directly from the tip or side of the hypha. Other asexual spores originate in the fragmentation of a hypha to form single cells that are released as spores; some of these have a thick wall surrounding the fragment. Yet others bud off the vegetative parent cell. In contrast to conidiospores, sporangiospores are produced directly from a sporangium.

Micrograph shows several long, thread-like hyphae stained blue. One hypha has a round sporangium, about 35 microns in diameter, at the tip. The sporangium is dark blue at the neck, and grainy white and blue elsewhere. Spores that have already been released appear as small white ovals.
Sporangiospores. This bright field light micrograph shows the release of spores from a sporangium at the end of a hypha called a sporangiophore. The organism is a Mucor sp. fungus, a mold often found indoors. (credit: modification of work by Dr. Lucille Georg, CDC; scale-bar data from Matt Russell)

Source:

Clark, M., Douglas, M., Choi, J. Biology 2e. Houston, Texas: OpenStax. Access for free at: https://openstax.org/details/books/biology-2e

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