Note on Reproduction in Mucor

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Vegetative reproduction

Vegetative reproduction takes place by fragmentation of hypha.

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Fig. Mucor - Different types of vegetative reproduction in fungi.

Asexual reproduction

Asexual reproduction takes place by formation of asexual spores like sporangiospores, chlamydospore, oidia.

Sporangiospore(Aplanospore):

Mucor mostly reproduces asexually by the formation of sporangiospores. Sporangiospores is produced inside sporangium at the tip of sporangiophore.

In favourable condition, sporangiospores are formed. In favourable condition prostrate hypha develop erect hypha and accumulation of more nuclei and cytoplasm takes place at the tip of an erect hypha. Swelling of the tip of erect hypha occurs and young sporangium is formed. Then differentiation of cytoplasm takes place. Peripheral fertile cytoplasm with many nuclei and dense cytoplasm is called sporeplasm and central part with few nuclei is called is called columella which is dome shaped sterile part. Cleavage occurs in sporeplasm which separates much mass of cytoplasm with few nuclei than the wall formation takes place around it that results in the formation of many thin-walled multinucleate spores called sporangiospores. Sporangiospore is yellowish brown in colour.

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fig:Asexual reproduction by sporangium

Dispersal of sporangium:

When the sporangium is matured dome shaped sterile part of columella swells up and this creates pressure on the wall of sporangium due to which bursting of sporangium occurs. Sporangiospores are release in the air as dark powdery form when they obtain suitable substratum they germinate immediately without resting period.

Chlamydospore:

They are thick-walled resting spore formed in unfavourable conditions.In unfavourable condition mature hypha become septed and accumulation of nuclei and cytoplasm takes place at the septed part than the thick wall is formed around it and change into the chlamydospore. They undergo resting period. In return of favourable condition germination of chlamydospore start and give rise to new mycelium.

Oidia:

In aquatic species of mucor, where their is high acidity and more sugar-rich substance hypha become septed than septed portion become round in shape and separate from the parent hypha. These are thin walled asexual spore called oidia.

Sexual reproduction

In mucor sexual reproduction takes place by gametangial conjugation. Some species are homothallic(conjugation takes place between hypha of same species)and heterothallic(conjugation occurs between hypha of opposite strain). Sexual reproduction takes place at the end of growing season.

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Mucor - Different stages in the sexual reproduction.

Two hyphae of opposite strain come in contact with each other and develop short outgrowth called protuberance. Accumulation of cytoplasm and nuclei takes place at the protuberance. Then swelling occur in each protuberance which forms progametangium. A septum is formed in each gametangium which separates terminal fertile more nucleated part into gametangium and basal sterile more vacuolated part into suspensor. Each gametangium work as canoe gamete and fusion of co Eno gametes takes place. Firstly plasmogamy occurs then karyogamy occur which result in the formation of diploid zygote. Zygote enlarges in size and get surrounded by the thick-walled warty structure and change into a zygospore. Zygospore is dark black in colour and has two covering layer. The outer layer is exosporium and the inner layer is endosporium. Zygospore is resting spore, it undergoes resting period.

Germination of Zygospore:

In return of favourable condition, zygospore starts to germinate. Before germination, it undergoes meiosis cell division and it forms many haploid nuclei of both strains. Among these haploid nuclei, single haploid nucleus remains functional other degenerates. That single functional haploid nucleus undergoes mitosis cell division and produces many haploid nuclei of same strains. In germination, exosporium gets burst and endosporium come out as germ tube. Germ tube produces germ sporangium at its tip. Inside germ sporangium, their are many haploid spores called germ spores. Germspore comes out by bursting germ sporangium and germinate and develop into new mycelium.

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fig:Mucor - Lifecycle

  • Mucor mostly reproduce asexually by formation of sporangiospores. 
  • Sporangiospore are produce inside sporangium at the tip of sporangiophore.\
  • Peripheral fertile cytoplasm with many nuclei and dense cytoplasm is called sporeplasm and central part with few nuclei is called is called columella.
  • In mucor sexual reproduction takes place by gametangial conjugation.
  • Two hypha of opposite strain come in contact with each other and develop short outgrowth called protuberance. 
  • A septum is formed in each gametangium which separates terminal fertile more nucleated part into gametangium and basal sterile more vacuolated part into suspensor. 

 

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makshye narayan sainju

when to comes sperm for born in it?


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