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DEUTEROMYCETES : REPRODUCTION

REPRODUCTION OF DEUTEROMYCETES   

 

Often referred to as molds, Deuteromycetes are ” Second Class ” fungi that carry no sexual state and reproduce via mitosis by producing special spores called conidia (sing. conidium). Anamorph is the state of asexual fungi. Due to the asexual reproductive mechanism, this class of imperfect fungi belongs to the artificial fungi, which have approximately 15,000 species.

The fungi that do not display a sexual phase are imperfect fungi. Deuteromycetes reproduce in a variety of ways. Reproduction is strictly asexual which mainly occurs by the production of asexual conidiophores . Spores or Conidia is one such from that grows directly on mycelium or on specialized mycelial cells called conidiophores. A conidium is a non-motile, asexual spore formed at the tip or side of a sporogenous cell.

Some of the Deuteromycetes also produce spores other than conidia. In addition to producing conidia, some of the Deuteromycetes also produce sterile mycelia and no conidia at all. These sterile mycelia may or may not produce sclerotia.

The conidial forms produce conidia on conidiophores arising directly from the somatic hyphae which may be hyaline or bright-coloured. The somatic hyphae may be loose;separate; innate or not; or closely aggregated to form sporogenous structure, such as acervulus, sporodochium and synnema. Besides these conidia may also be produced in complex structure like, pycnidia.

  MODE OF REPRODUCTION

In the form-class Deuteromycetes, there are many types of conidia produced within the form-class Deuteromycetes. Conidia may be spherical, ovoid, elongated, cylindrical, thread-like, spirally curved, star shaped, and so on. Conidia may also be one-celled to many celled. Conidia produced in chains are said to be Catenulate. But there are also forms where the conidia are produced in the centre of the conidiophores and pushed out successively from an opening at the apex. These are known as endoconidia.

Figure 1 :

 Types of conidia and conidiophores

 

ASEXUAL FRUCTIFICATION: 

  There are 4 types of asexual fructification. These are-

  1. Acervulus
  2. Sporodochium
  3. Synnema
  4. Pycnidia

Acervulus: noun, plural a-cer-vu-li [uh-sur-vyuh-luhs],

The conidia develop on conidiophore, and both these structure form the fruiting body of fungus called acervulus.

  • An acervulus is typically a flat or saucer-shaped bed of short conidiophores growing side by side and arising from a more or less stromatic mass of hyphae.
  • An acervulus ( pl. acervuli) is an asexual fruiting body consisting of a mat of hyphae that give rise to short-stalked conidiophores.
  • This asexual body that erupts through the epidermis of host plants parasitised by mitosporic fungi of the form order Melanconiales.
  • A small cushionlike structure produced by certain parasitic fungi, containing a mass of asexually produced spores.
  • An acervulus that always developed below the epidermis of the host tissue, it bears conidiophores ( specialized filaments or hyphae) that form conidia ( spores)
  • Also called acervulus cerebri, brain sand ,sandy calcifications occuring in the brain, particularly around the pineal gland.

Figure 2 : Acervulus

SPORODOCHIUM : 

  • An acervulus may develop a compact mass of conidiophores on a well-marked basal stroma or mass of hyphae producing a structure known as sporodochium.
  • A sporodochium (pl.sporodochia) is a small, compact stroma usually forms on host plants parasitised by mitosporic fungi of the form order Tuberculariales.
  • This stroma( cushion shaped) bears conidiophores on which the asexual spores or conidia are formed.
  • The conidiophores are packed tightly together and are generally shorter than those composing a synnema

   Figure 3 : Sporodochium 

SYNNEMA

  • A synnema ( pl. synnemata, also coremia;derivation: ” Threads together”) is a large, erect reproductive structure borne by some fungi , bearing compact conidiophores.
  • Conidia may be formed along the length of the synnema or only at it’s appex.
  • Some synnemata the ” stalk-like ” portion is longer in comparison to the branched top and the entire structure resembles a long handed feather cluster.
  • Synnema forming an elongated stem or bristle like structure ( called a fasicle, this being latin for ” a bundle” )
  • It may have many hyphal strands in their structure and be fleshy, hard or brittle in structure.
  • The apical portion of conidiophores that make up the synnema are separate and radiate outward, often producing a mucus slime in which the conidia are trapped ( perhaps awaiting insect dispersal ) .

Figure 4 ; Synnema

PYCNIDIA : noun, plural pyc-nid-i-a [pic-nid-ee-uh]

  • A pycnidium (pl. pycnidia) is an asexual fruiting body produced by mitosporic fungi in the form of order Sphaeropsidales.
  • A pycnidium is a globose or flask-shaped pseudoparenchymatous structure that is lined on the inside with conidiophores.
  • Conidia are released via pore in the wall of the pycnidium.
  • Pycnidia contains minute spores called Pycniospores.
  • The pycnidia may be completely closed or may have an opening ( ostiole) through which conidia escape.
  • The ostiole may be narrow or wanting, or it may be very large, round, irregular.
  • They very greatly in size, shape,and colour, as well as in the consistency of the delicate pseudoparenchymatous wall; they may be superficial or sunken in the substrate .
  • Picnidium may be uniloculate, simple or labyrinthiform.

 

Figure 5 : Conidia

 

Reference:

  • Introductory mycology by Alexopoulos and Mims
  • Class lecture by Shamim Shamsi ma’am
  • Feature image from source
  • Information from biology discussion

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