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SLIME MOULDS OR CONSUMER DECOMPOSER PROTISTS(Protistan fungi)

1.They were included in class myxomycetes of fungi in two kingdom classification. Mycologists include them in gymnomycota.

2.Usually non living , creeping over debris.

3. Protoplast not covered by cell wall in vegetative stage.

4. Lack chlorophyll, have saprobic mode of nutrition.

5. Somatic body – free living, multinucleate, diploid mass called Plasmodium.

6. Movement occurs by pseudopodia.

7. Reproduces both sexually and asexually.

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LIFE CYCLE OF AN ACELLULAR SLIME MOULD

  1. During life cycle, they are amoeboid and non cellulosic but spores have cellulosic wall.
  2. Amoeboid plasmodial stage resembles protozoa and spore forming nature is like fungi.
  3. Under unfavourable conditions, entire plasmodiumforms many fructifications or fruiting bodies(polycentric) .
  4. Diploid protoplast forms haploid spores by meiosis.
  5. On germination, spores produce biflagellated swarm cells as gamete
  6. Diploid zygote directly forms the plasmodium which becomes multinucleate by repeated mitotic divisions.
  7. Sexual reproduction is isogamous.

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CELLULAR SLIME MOULDS

Common cellular slime mould, Dicotyostelium, is a colonial form in which hundreds of uninucleate , haploid amoeboid cells are aggregated without any fusion and a colony is formed named pseudoplasmodium.

Under exhausted food supply and stimulation of cAMP and chemical acrasin, many cells come close by chemotactic movement . Pseudoplasmodium exhibits primitive form of multicellularity and division of labour. So these are called communal slime moulds. On these basis, cellular slime moulds are regarded as advanced protist and primitive fungi.

During unfavourable conditions, the myxamoebae may form a cyst called microcyst for perennation and dispersal.

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1. Under dry conditions, the pseudoplasmodium produces stalked sporocarp, which may be branched or unbranched , each branch bearing single sporangium terminally.

2. Within the sporangium, amoeboid cells become rounded to secrete a spore wall around.

3. On the approach of favourable conditions, spores are liberated.

4. Each spore germinates by rupturing cellulosic wall and they may live independently, multiply by repeated mitotic division or get aggregate to form pseudoplasmodium.

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By taking example of slime moulds, we can justify that Protista forms a connecting link with plants, animals and fungi.

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  • FUNGI LIKE FEATURE – Formation of fruiting bodies
  • PLANT LIKE FEATURE –Cell wall around spores
  • ANIMAL LIKE FEATURE- Plasmodium without cell wall.