Reproduction in Fungi- Part-2: Asexual Reproduction

Fungi reproduce by vegetative, asexual and sexual methods. This post describes the various types of Asexual Reproduction in Fungi. About 20% fungi propagate only by asexual means. Asexual reproduction take places during favorable condition by the formation of a variety of spores. Such spores produced by asexual reproduction are called mitospores. Spores may be unicellular (Aspergillus, Penicillium) or Multicellular (Alternaria, Cercospora)

Asexual Reproduction in Fungi

Ø  Based on the number of cells in spores, asexual spores of fungi are classified into:

1. Amerospore: one celled spores

2. Didymospore: two celled spores

3. Phragmospore: spore with two or more transverse septa

4. Dictyospores: spores with one or more transverse and vertical septa

5. Scolecospores: vermiform or filiform (thread like) shaped spores

6. Staurospores: stellate or spores with radiating arms

7.  Helicospores: spirally coiled spores

Ø  The number of cells in spores have immense taxonomic importance for the identification and classification of fungi

Ø  The spores may be endogenous when  enveloped in pycnidia or sporangia (Mucor, Rhizopus) or they may be exogenous when developed on sporophores or conidiophores (Aspergillus, Penicillium)

Ø  Spores produced in specialized sacks called sporangia are known as sporangiospores

Ø  Spores produced on the tip of hyphae either singly or in group, is called conidiospores

Ø  Common asexual spores of fungi are:

(1).  Zoospores

(2).  Aplanospores

(3).  Conidiospores

(4).  Chlamydospores

(5).  Pycnidiospores

(6).  Oidia

(1). Zoospores

Ø  Zoospores are a type of sporangiospores (endospore)

Ø  They are motile spores with flagella

Ø  Zoospores are usually produced by lower groups of fungi

Ø  Example: Phythium, Phytopthora

Ø  Based on the number and position of flagella, there are three types of zoospores in fungi

(1). Posteriorly uni-flagellated zoospores: zoospores with posteriorly placed whiplash type of flagella (example: Chytridiomycetes)

(2). Anteriorly uni-flagellated zoospore: zoospores with anteriorly placed tinsel type of flagella (Example: Hypochytridiomycetes)

(3). Biflagellated zoospores: zoospores with two anteriorly or laterally attached flagella, one is whiplash and the other is tinsel type (Example: Oomycetes)

(2). Aplanosores

Ø  Aplanospores  are non-motile spores, produced in sporangia (endospores)

Ø  Usually they are round in shape with one or many nucleus

Ø  Most of the cases, aplanospores are produced in large numbers

Ø  They can germinate by the formation of germ tube in the favourable conditions

(3). Conidia or conidiospores

Ø  Conidia are non-motile spores

Ø  They are produced in single or in chain on special type of hyphae called conidiophore

Ø  Conidia are exospores since they are produced exogenously

(4). Pycnidiospores

Ø  They are very small spores produced in special structures called Pycnidia

Ø  Pycnidiospors are usually produced by members of fungi imperfectii (Deuteromycetes) and many lichens

Ø  They are usually single celled, thin walled, however multicellular pycnidiospres are also found

(5). Chlamydospores

Ø  Chlamydospores are thick walled resting spores

Ø  They store food materials (Eg. Ustilago)

(6). Oidia

Ø  Hyphae breaks up to small pieces each develops into single called oidia

Ø  Oidia are generally thin walled and small

Ø  They do not store food material

Ø  Oidia germinate immediately after liberation (Eg. Coprinus)

Ø  Fungal component in some lichen can reproduce by the formation of oidia

Learn more: Vegetative Reproduction in Fungi

Learn more: Sexual Reproduction in Fungi

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