The slime molds and water molds used to be considered types of fungus. They are, however, completely unrelated to the true fungi and are good examples of convergent evolution. Convergent evolution occurs when two organisms develop similar characteristics because of adaptations to similar environments and yet are not related on a molecular level (figure 12.19). Show Acellular and Cellular Slime MoldsThere are two groups of slime molds, the acellular slime molds and the cellular slime molds. The slime molds are terrestrial organisms living on soil, leaf litter, or the surfaces of decaying leaves or wood. They are non-motile, and reproduction depends on the formation of spores that can dispersed. Acellular slime molds are widespread and readily visible in their natural environment. Following sporulation and germination of the spores, ameboid cells fuse to form a myxameba. The nucleus of this ameba divides repeatedly, forming a multinucleated stage called a plasmodium. The plasmodium oozes like slime over the surface of decaying wood and leaves. As it moves, it ingests microorganisms, spores of other fungi, and any other organic material with which it comes in contact. Eventually the plasmodium is stimulated to form a spore-bearing fruiting body, and the process begins again (figure 12.20a). The cellular slime mold has a vegetative form composed of single, ameba-like cells. When cellular slime molds run out of food, the single cells congregate into a mass of cells called a slug that then forms a fruiting body and spores. These fruiting bodies and spores look very much like fungal fruiting bodies and spores (figure 12.20b). 314 Chapter 12 The Eukaryotic Members of the Microbial World Animals - Choanoflagellates Spores -Fungi- - Zygomycetes -Ascomycetes -Basidiomycetes -Chytridiomycetes ■ Land plants -Chlorophytes (green algae) ■ Cryptomonads Rhodophyta (red algae) Stramenophiles- ■ Chrysophyta (golden brown algae and diatoms) - Phaeophyta (brown algae) Oomycetes (water molds) Ciliates ■ Pyrrophyta - dinoflagellates ■ Apicomplexans Cellular slime molds Acellular slime molds Entamoebids Amoeboflagellates ■ Kinetoplastids Euglenoids Parabasalians ■ Diplomonads - Microsporans Bacteria Figure 12.19 A Phylogenetic Scheme of Eukaryotes Based on rRNA Sequence Comparisons The slime molds and water molds are highlighted in blue. Fruiting bodies release spores Spores Fruiting bodies release spores  Myxamoebae Fruiting body Myxamoebae Fruiting body Figure 12.20 Slime Molds (a) Life cycle of an acellular slime mold. (b) Fruiting body of a cellular slime mold. Figure 12.20 Slime Molds (a) Life cycle of an acellular slime mold. (b) Fruiting body of a cellular slime mold. Slime molds are important links in the food chain in the soil. They ingest bacteria, algae, and other organisms and, in turn, serve as food for larger predators. Slime molds have been valuable as unique models for studying cellular differentiation during their aggregation and formation of their fruiting bodies. Oomycetes (Water Molds) The oomycetes, or water molds, are members of a group of organisms known as heterokonts. The oomycetes do not have chlorophyll, whereas other heterokonts, which include the grass green algae, diatoms, and brown algae, have chlorophyll and other photosynthetic pigments. Oomycetes were once considered fungi because they look like fungi. They form masses of white threads on decaying material. They have flagellated re productive cells known as zoospores. Oomycetes cause some serious diseases of food crops. The late blight of potato (Phytophthora infestans) and downy mildew of grapes are included in this group. The late blight of potato was the cause of the potato famine in Ireland in the 1840s that sent waves of immigrants to the United States. Continue reading here: Multicellular Parasites Arthropods and Helminths Was this article helpful?
Slime molds belong to a 'primitive' class of fungi called Myxomycetes. It is a small group of organisms with only 700 species known worldwide. They are organisms that obtain their nutrients from dead or decaying matter and are most prevalent following extended periods of wetness. Slime molds can be found in lawns, flower beds, gardens, and anywhere organic matter is present. Spores germinate into structures that eventually merge together and form a large plasmodium, otherwise know as 'the blob' (Fig 1). A plasmodium is a shapeless growing mass that may reach two feet in diameter. In Georgia, slime molds differ from blue-gray in color to yellow, orange or black. Slime molds 'creep' along slowly but may travel up to several feet a day. Slime molds do not cause any direct injury to plants but may inhibit photosynthesis if the plasmodium is thick and persistent. As weather conditions dry, the plasmodium forms spore-producing structures and spores are blown by the wind to new locations to start the cycle over. These spore masses can appear as gray to black dusts on grasses or other plant materials. Slime molds are essentially harmless and are only considered a nuisance. Control does not require any chemicals and simply mowing over the lawn removes them from view. On mulch, raking or disturbing the slime mold with forceful water sprays is all that is needed. Spanish MossSpanish moss (Tillandsia usneoides) is an epiphytic plant found growing mainly on hardwoods throughout the Southeast. It is not a plant parasite and only uses the tree for support and protection (Fig 3). Instead, it makes its own food. Spanish moss has long slender stems that wrap around the tree allowing it to hang in the air (Fig 4). Tiny scale-like cups on the stems catch water and nutrients from the air thereby enabling the moss to undergo photosynthesis. The Spanish moss' water-catching ability allows it to be drought-resistant and survive extreme dry spells. Spanish moss does require sunlight and can be found on trees in decline or trees with small openings in the canopy. Even though Spanish moss does not directly affect trees, abundant growth may inhibit tree foliation and reduce photosynthesis. Spanish moss is relatively harmless to trees; however, if excessive growth is occurring, one may manually remove the moss and increase tree vigor with proper fertility and irrigation to increase foliation thereby preventing much needed sunlight for moss photosynthesis. LichensLichens are composite, symbiotic organisms made up from members of as many as three biological kingdoms . The lichen fungi cultivate partners that manufacture food by photosynthesis. Sometimes the partners are algae, other times cyanobacterium, formerly called blue-green algae. Some enterprising fungi exploit both at once. The alga or cyanobacterium converts sunlight and carbon dioxide to food for the lichen fungus and in return the lichen fungus protects the alga/cyanobacterium from drying out. The fungus obtains water and minerals from the air and the material it is growing on (Fig 5). The alga provides carbohydrates and vitamins. Some blue-green algae fix nitrogen that is used by both the alga and the fungus. Nitrogen is also obtained from bird excrement, organic debris, or plant leachate . It has been said that lichens are fungi that have discovered agriculture. Lichens are found on rocks, tortoise shells, window panes, and plants. As plants are stressed and begin to decline, the reduced canopy allows sunlight to enter and support photosynthesis for the lichen. The presence of lichens are often an indicator of poor plant health but it is never the cause (Fig 6). Lichens are harmless to plants and, if overall plant health is improved, the vibrant canopy should inhibit any sunlight available for lichen photosynthesis. MistletoeMistletoe is an evergreen parasitic plant found on a wide host range including alder, birch, cottonwood, maple, oak, and zelkova among others. Mistletoe obtains water and minerals from the host but it is not totally dependent. Leaves of the mistletoe contain chlorophyll and are capable of making their own food from carbon dioxide and water like other plants. Birds feed on the berries produced and excrete them to new hosts. When the seeds germinate, it grows through the bark and into the vascular system of the host where it obtains water and minerals (Fig 7). On younger plants, the older leaves will curve downward and droop. The bases of the affected stems enlarge, and the vascular system becomes brown. On older plants, symptoms are apparent from blossoming to fruit maturation. The first symptom is chlorosis of the older leaves, usually on only one side of the plant. A browning of the vascular tissue extends up the stem while the pith remains healthy (Figure 3). Gradually, the yellowing affects all of the plant, causing it to wilt during hot temperatures. Eventually the plants will die. The mistletoe grows slowly at first and it may be years before seeds are produced. Healthy trees are able to tolerate small mistletoe infestations, but individual branches may be compromised and susceptible to wind or cold injuries. Heavy infestations may reduce the overall plant health or kill a tree especially if the tree is already stressed from environmental factors (Fig 8). Since mistletoe takes several years to produce seed simply removing it will provide some protection. Mistletoe may also be pruned out one foot below the point of attachment. If the mistletoe is located on a main limb or trunk, removing the top of the mistletoe and wrapping the cut with an opaque plastic to prevent sunlight may be beneficial. In addition to these mechanical controls, the growth regulator ethephon may be used when the host is dormant. ReferencesCornell University Bertrand, B., and Hadden, J.F. 1992. Slime Molds, Spanish Moss, Lichens, & Mistletoe. The University of Georgia Cooperative Extension Service. Bulletin 999. Forestry Images Perry, E.J., and Elmore, C.L. 2002. Mistletoe . University of California Pest Notes. Publication 7437. Rimelspach, J., and Boehm, M. 1995. Slime Molds on Turfgrass . Ohio State University Extension. Bulletin HYG-3074-96. University of Florida Status and Revision History Are water molds and slime molds related to fungi?A sporangium (pl., sporangia) is a plant or fungal structure that produces and contains spores. However, slime molds and water molds, which are the fungus-like protists, are now recognized as being different to fungi. The small, slimy-looking fungus-like protists differ from fungi in many ways.
Are slime molds considered fungi?Slime molds were formerly classified as fungi but are no longer considered part of that kingdom. Although not forming a single monophyletic clade, they are grouped within the paraphyletic group Protista.
Are water molds a fungi?water mold, (order Saprolegniales), also spelled water mould, order of about 150 species of filamentous funguslike organisms (phylum Oomycota, kingdom Chromista). Many water molds live in fresh or brackish water or wet soils.
Why are slime molds and water molds not classified as fungi?Though they were formally classified as fungi, slime molds do not have chitin in their cell walls and have a diplontic life cycle (Figure 5.2. 1. 12). These organisms move about as amoebae engulfing bacteria (unlike fungi, who digest food externally).
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Are slime molds and water molds fungi?
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