(TAXONOMIC STATUS AND CLASSIFICATION of Slime Molds)
Slime molds (or moulds) are a group of eukaryotic organisms which have confused the classical mycologists and were therefore included in the fungal kingdom. Antony De Bary (1887) considered slime molds as animals or closely related to animals and referred them as Mycetozoa. His view was supported by Bessey (1950). But due to the occurrence of fungal like spores and sporangia some mycologists like Alexopoulos, Martin, Ainsworth included them under the fungal kingdom but not as true fungi. Alexopoulos (1962) included the slime molds in the subdivision Myxomycotina of the division Mycota (The fungal kingdom). Ainsworth also kept these organisms under the division Myxomycota of the kingdom fungi. Martin included them under the subdivision Myxomycotina of the division Mycota similar to that of Alexopoulos. But Martin believed that this group might have originated from a protozoan-like ancestor and departed from the main evolutionary line of the fungi.McLauglin and MacLaughlin (2000) have kept these group of organisms under Pseudomycota in super kingdom Mycota and divided this into three divisions. Webster and Weber (2007) have kept the lime molds in the two subdivisions Myxomycota and Plasmodiophoromycota in the Kingdom Protozoa. In the modern classification slime molds are well recognized as protozoans due to their unicellular characters, lack of cell wall and phagocytic modes of nutrition and have been grouped under the kingdom Protozoa. These organisms have been segregated in four phyla of the kingdom Protozoa and they are: Phylum Plasmodiophoromycota, Phylum: Myxomycota, Phylum: Acrasiomycota and Phylum Choanozoa.
The classification of slime molds is still under changes. The modern view favours the idea that there are multiple kinds of slime molds that are not closely related. While some group of workers recognized three types, some workers recognize six types of slime molds and grouped accordingly.
The six types are:
(i) Plasmodial (or true) slime molds (the Mycomycota or Myxogastria
These are single celled amoebo flagellates that combine to make plasmodia with thousands
nuclei. They produce different kinds of fruiting bodies, the most common is a sporang
type with spores. E.g., Physarum.
(ii) Cellular slime molds (the Dictyostelids or Dictyosteliomycota). These are amoeb single-celled organisms that combine to make larger scale single organisms in whi individual cells remain distinct within the 'pseudoplasmodium' they have formed. The why they are cellular rather than plasmodial. (E.g., Dictyostelium). (iii) The Protostelia (Microscopic slime molds): These were first known in 1960s and are le
known than the above two like plasmodial or 'true' slime molds, they form a
plasmodium.
(iv) The Acrasids or Acrasiomycota: These organisms function like cellular slime molds, br molecular and ultra structural evidence indicate they are evolutionarily unrelated to o mycetozoa. They have often been classified with the Dictyostelids within the cellular sli molds but the Dictyostelids are soil organisms whereas these are found on dead plants (E.g., Fonticula).
(v) The Labyrinthulomycota (or slime nets). Although they are called slime molds they dont seem to be closely related to other kinds of slime molds and form a separate phylum in s classifications. They form a net plasmodium and mostly marine in nature.
(vi) The plasmodiopheromycota: These are true or plasmodial slime molds but differ from myxomycota in that the myxomycota are free living whereas these are parasitic on plants a fungi. They are considered by some to be an entirely different phylum.
However, mostly the plasmodial slime molds, the cellular slime molds and the slime nes (Labyrinthulomycota) are very common and have a similar life cycle and resemble to fungi.
