Acellular Slime Moulds Plasmodial Slime Moulds Habitat Structure and Life Cycle, Fruiting Bodies, Sporen, Germination, Meiosis, Fructifications, Myxamoeba

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Home >> Microbiology >> Eukarya Eukaryotic-Microorganisms >> Acellular Slime Moulds Plasmodial Slime Moulds Habitat Structure and Life Cycle

Acellular Slime Moulds Plasmidial Slime Moulds Habitat Structure and Life Cycle

The acellular slime moulds are commonly found on dead and decaying leaves, twigs, logs of wood and the other decaying vegetable matter.

They prefer to grow in damp places rich in decaying vegetable matter in the forests a little after and during the rainy seasons.

Somatic diploid phase is wall-less multinucleate protoplasm called plasmodium.

It may be coloured variously. Plasmodium creeps over the surface of substratum with the help of pseudopodia.

The chief mode of nutrition of plasmodium is saprotrophic, absorbing the organic food from the decaying organic matter (substratum of plasmodium). Plasmodium also feeds on bacteria, protozoa, spores of fungi and other microorganisms through ingestion and engulfing (i.e., phagotrophic or holozoc nutrition).

Under unfavourable conditions such as drought or too much cold, the plasmodium divides to form many multinucleate cysts.

Sometimes even whole plasmodium forms a hard dormant structure called sclerotium.

On the return of favourable conditions, the cyst or the sclerotium liberates the multinucleate diploid plasmodium.

Thus, these structures serve for perennation.

Life Cycle of an Acellular Slime Mould

Life Cycle of an Acellular Slime Mould

1. Fruiting Bodies	9. Diplophase
2. Sporen	10. Haplophase
3. Germination	11. Myxamoebae Plasmogamy
4. Meiosis	12. Swarm Cells (N)
5. Fructifications	13. Older Plasmodium (2N)
6. Myxamoeba	14. Young Plasmodium (2N)
7. Cell Division	15. Karyogamy
8. Beginning of Fruiting	16. Zygote (2N)

(i) Formation of Sporangia. When the plasmodium reaches a certain stage of maturity or the food supply is nearly exhausted, the contents of plasmodium concentrate at one or more places forming papilla-like mounds that grow into sessile or stalked sporophores.

Each sporophore bears one or more sporangia (= fruiting bodies). Each sporangium is surrounded by a hard and brittle wall-like layer, the peridium.

(ii) Formation of Spores. The numerous diploid nuclei in the sporangium undergo meiotic division. The multinucleate protoplasm of the sporangium undergoes cleavage to form uninucleate tiny segments.

Each uninucleate tiny segment becomes rounded and secretes a cell wall to become spore. The sporangium also develops a system of threads called capillitium.

(iii) Liberation of Spores from the Sporangia.

When fully mature, the wall of the sporangium bursts to release the spores. The spores are dispersed by air. A large number of spores are often present in the air. Spores of some species such as Fuligo septica cause allergic reactions.

(iv) Germination and Sexual Reproduction.

After falling on a suitable substratum, each spore germinates only when water is available. On germination, a spore generally releases one biflagellate, spindle-shaped swarm cell or a non-flagellate myxamoeba. The myxamoebae feed on bacteria and yeasts and multiply in number. The swarm cell swim about actively and finally fuse in pairs at the posterior non flagellate ends to form zygotes.

(v) Formation of Plasmodium.

The zygote creeps over the substratum and feeds on bacteria, yeasts and the other organic matter. It grows in size. The diploid nucleus of zygote undergoes repeated mitotic divisions. As a result, the zygote gradually changes into a multinucleate amoeboid structure, the plasmodium. The plasmodium repeats the life cycle.

Examples. Physarum, Physarella, Fuligo. Dictydium. Lycogala, Tubifera.

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