The Zygomycota is comprised of approximately Zygomycota asexual reproduction pictures of microscopic fungi
Zygomycota asexual reproduction pictures has traditionally been divided into two classes, Zygomycetes and Trichomycetes. Zygomycota asexual reproduction pictures two classes represent a very diverse group of microscopic fungi that have mostly been characterized Zygomycota asexual reproduction pictures the earliest group of Fungi evolved, as evidenced by members that have mostly coenocytic hyphae that lack a complex fruiting structure during reproduction, but diverged later than the Chytridiomycota, as the earliest group of terrestrial fungi White, et al.
Reproduction mostly occur asexually by nonmotile but see Olipidium brassicae in White, et al. Because only one zygospore is produced per zygosporangia, the terms have been used interchangeably. However, not all species are known to reproduce, sexually.
In the traditional sense, some taxa within the Trichomycetes have recently been removed from the Zygomycota and are no longer classified as Fungi. The Trichomycetes are a unique group of organisms that form a symbiotic relationship with arthropods and are found within their hindgut or exoskeletons Benny and O'Donnell, Since these
Zygomycota asexual reproduction pictures are not known to harm or benefit their hosts,
Zygomycota asexual reproduction pictures relationship is said to be commensal.
They form short hyphal growth that are non-septate, with sporulating structures that are derived from basal cells that attach Zygomycota asexual reproduction pictures the host and Zygomycota asexual reproduction pictures sporangiospores at their tips.
Although this would appear to be a rather unique habitat, it does not exclude the possibility that morphologically similar organisms, adapting to the same environment have evolved via convergent evolution. Some taxa have been demonstrated to not only be incorrectly classified as members of the Zygomycota, but are not even Fungi. As early asTrotter and Whistler determined that the cell wall of Amoebidium parasiticum was mostly galactosamine and galactose and not chitin.
Since that time, this species, as well as all members of the orders Amoebidiales and Eccrinales have gone through molecular analyses and have been reclassified as protozoans, in the class Mesomycetazoae Cavalier-Smith ; Benny and O'Donnell and Cafarno The Phylum Glomeromycota of the Zygomycetes was traditionally classified in the family Endogonaceae, within the Mucorales. It was later elevated as an order, i.
Glomerales, by Morton and Benny and eventually to the level of phylum, i. The phylum is characterized by forming obligate endomycorrhizal relationships Zygomycota asexual reproduction pictures a wide variety of plants. As such, they have become economically important in conservation of plants, plants growing in
Zygomycota asexual reproduction pictures area and plant diseases.
They have non-septate hyphae where large asexual spores are borne. Sexual reproduction have not been observed in this group of Fungi. We will not cover this group as a separate phylum, but Zygomycota asexual reproduction pictures will cover them as an example of symbiotic relationships in the Fungi in our last lecture. The remainder of the Zygomycota have been tentatively classified into various clades by different authors Nagahama, et al. At this time there is intensive research being carried out in this phylum and it is still uncertain
Zygomycota asexual reproduction pictures to whether the remainder of the taxa represent a monophyletic group in this phylum.
summary of the clades recognized by White, et al. Covering each of the different clades will not be possible because of time constraints and is also beyond the scope of this course. Instead, we will use the Mucorales Class Zygomycetes as representative of this phylum to illustrate some of the variations in asexual reproduction present in this order. Rhizopus stolonifer will be used as the representative species in describing the development of the asexual and sexual cycles and will be followed up with variations of
Zygomycota asexual reproduction pictures reproductions present in this order: Typically, most members of the Zygomycota produce their asexual spores in sporangia.
This phylum is the only group of terrestrial fungi in which asexual spores are borne in this matter. Within the sporangium proper are non-flagellated spores called Zygomycota asexual reproduction pictures referred to as just spores, and a columella.
Development of the Sporangium of Rhizopus
Zygomycota asexual reproduction pictures. The development of the sporangium begins with the production of upright sporangiophore, above the root-like rhizoids Fig.
When young, sporangiophores appear to be upright hyphae. After elongating to a pre-determined height, the tip of the sporangiophore will swell and become globular in shape. When mature, the globular tip will become the sporangium. Initially, the density of the nuclei will be uniform in this area Zygomycota asexual reproduction pictures. However, the cytoplasm and nuclei becomes more dense in the swollen area as the the protoplasm below becomes highly vacuolated with few nuclei.
Between the dense and vacuolated protoplasmic layers, a dome shaped layer of vacuoles appear Fig. These vacuoles will become flattened and fused, separating the two layers or protoplasm. A cell wall is then secreted by this layer that completely Zygomycota asexual reproduction pictures the dense from the vacuolated protoplasm and form the dome-shaped columella Fig. The densely nucleated protoplasm now develops numerous branching furrows that initially cleaves the protoplasm into small, polyhedral, multinucelated that will eventually round up, secrete cell Zygomycota asexual reproduction pictures to become the asexual spores Figs.
The remaining cytoplasm, outside the spore walls, dries out and at maturity the sporangial walls is so fragile that will rupture the slightest disturbance and release the spores. Variations in asexual reproductive structures. There is a great deal of variation that occurs in the of the Mucorales. Below are a few of the more common variations: Sporangia in this species are borne around the surface of vesicles that form on the tips of sporangiophores Figs.
The sporangia are cylindrical, with the spores within borne in a column.
Sporangia of this type are specifically referred to as merosporangia. Sporangioles are borne from dichotomous branches derived from the sporangiophores. A terminal, multispored sporangium, with a columella may also be borne on the same sporangiophore Zygomycota asexual reproduction pictures. Sporangioles contain spores and do not have columellas Figs.
Sporangioles in this species are borne around the surface of vesicles that formed terminally and laterally, on the tips of sporangiophores Figs However, longitudinal sections of sporangioles clearly indicate that a sporangiole wall encloses the true spore wall. The specific epithet name "echinulata" describes the spiny appearance of the sporangiole walls Fig. Designation of male and female are not utilized here because the mycelium of each strain is identical in appearance. As the mycelia of Zygomycota asexual reproduction pictures mating strains begins to grow towards one another, a phermone, trisporic acidinduces formation of progametangia Fig.
Nuclei will migrate into the apices of the progametangia and septa will form that will trap the nuclei in the terminal cells. The terminal cells are
Zygomycota asexual reproduction pictures called because they are similar in size Zygomycota asexual reproduction pictures appearance, and the remainder of what was the progametangia are the suspensors Fig. Fusion of gametangia will take place, resulting in plasmogamy.
As karyogamy is occurring, formation of a dark, thick cell wall will form around the zygote, which may now be referred to as the zygosporangium or zygospore Fig. The zygospore is a resistant stage that is not dispersed. It remains dormant until conditions favoring growth returns. The zygospore will then germinate to give rise to Zygomycota asexual reproduction pictures single sporangium that is morphologically identical to those described above.
The formation of the zygospore is the unifying characteristic of the fungi in this phylum where their sexual cycle is known. I have posted a time lapsed video on YouTube of the development of the zygosporangium, in the genus Phycomyces.
If differs from R. Some species do not require different mating strains in order for sexual reproduction to occur and are self fertile. Such species are said to be homothallic. A pair of progametangia in this species are borne on the same sexual hyphae.
While similar in morphology, one progametangium is several times larger than the other as will be the resultant gametangia and suspensors derived from these progametangia. Because of the differences their sizes, the larger and smaller structures are referred to as Megaprogametangiamegagametangia and megasuspensorsand microprogametangiamicrogametangia and microsuspensorsrespectively.
The illustration of zygosporangium development in Fig. formation of zygospores is defining characteristic of the fungi in this phylum where their sexual cycle is known. Zygomycetes and their spores.
National Museums of Canada. Amoebidium parasiticum is a protozoan, not a Trichomycete. Eccrinales Trichomycetes are not fungi, but a clade of protists at the eqarly divergence of animals and fungi.
Molecular Phylogenetics and Evolution. A revised six-kingdom system of life. Zygosporogenesis in Zygorhynchus heterogamuswith a proposal for standarization of structural nomenclature.
Das Pflanzenreich Hausschatz des Wissens. Phylogeny of the Glomerales and Diversisporales Fungi: Glomeromycota from actin and elongation factor 1-alpha sequences. Academic Press, New York. Fungal Genet Biol Phylogenetic relationships among the Harpellales and Kickxellales. Delimitation Zygomycota asexual reproduction pictures Umbelopsis Mucorales, Umbelopsidaceae fam. Revised classification of arbuscular mycorrhizal fungi Zygomycetes: Phylogenetic divergence of the entomophthoralean fungi: A new fungal phylum, the Glomeromycota: Mol Phylogenet Evol Chemical composition of the cell wall of Amoebidium
Zygomycota asexual reproduction pictures. Phylogeny of the Zygomycota based on nuclear ribosomal sequence data.
Zygomycota The Zygomycota is comprised of approximately species of microscopic fungi that has traditionally been divided into two classes, Zygomycetes and Trichomycetes.
Members of this Zygomycota asexual reproduction pictures have branched coenocytic mycelium that grow rapidly in culture, with an abundance of aerial mycelium. Septa may be present
Zygomycota asexual reproduction pictures they delimit reproductive structures.
They are borne on branched or unbranched stalks referred to as sporangiophores. Sexual reproduction, where known, occurs by formation of zygospores. However, many species are not known to produce zygospores and is the reason why asexual reproductive structures are utilized in identification.