Protista - Slime Molds And Water Molds

The fungus-like protists resemble the fungi during some part of their life cycle. These organisms exhibit properties of both fungi and protists. The slime molds and the water molds are members of this group. They all obtain energy by decomposing organic materials, and as a result, are important for recycling nutrients. They can be brightly colored and live in cool, moist, dark habitats. The slime molds are classified as either plasmodial or cellular by their modes of reproduction. The plasmodial slime molds belong to the phylum Myxomycota, and the cellular slime molds belong to the phylum Acrasiomycota.

The plasmodial slime molds form a structure called a plasmodium, a mass of cytoplasm that contains many nuclei but has no cell walls or membranes to separate individual cells. The plasmodium is the feeding stage of the slime mold. It moves much like an amoeba, slowly sneaking along decaying organic material. It moves at a rate of 1 in (2.5 cm) per hour, engulfing microorganisms. The reproductive structure of plasmodial slime molds occurs when the plasmodium forms a stalked structure during unfavorable conditions. This structure produces spores that can be released and travel large distances. The spores land and produce a zygote that grows into a new plasmodium.

The cellular slime molds exist as individual cells during the feeding stage. These cells can move like an amoeba as well, engulfing food along the way. The feeding cells reproduce asexually through cell division. When conditions become unfavorable, the cells come together to form a large mass of cells resembling a plasmodium. This mass of cells can move as one organism and looks much like a garden slug. The mass eventually develops into a stalked structure capable of sexual reproduction.

The water molds and downy mildews belong to the phylum Oomycota. They grow on the surface of dead organisms or plants, decomposing the organic material and absorbing nutrients. Most live in water or in moist areas. Water molds grow as a mass of fuzzy white threads on dead material. The difference between these organisms and true fungi is the water molds form flagellated reproductive cells during their life cycles.