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In this article we will discuss about the sexual reproduction in coprobia with the help of suitable diagrams.
It varies in different species of Humaria. In Coprobia granulatus only the female sex organ is developed. It is called the ascogonium. The antheridium is lacking. The mature ascogonium is a multinucleate, oval structure. It has no trichogyne.
It is borne at the end of a side branch, the archicarp (female branch) arising from a mycelial hypha. The archicarp consists of a long multicellular stalk bearing the ascogonium at its top.
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The mature ascogonium is reported to contain about 600 to 1400 female nuclei. Gwynne Vaughan and Barnes have reported that young ascogonia in a single spore culture perish.
They undergo no further development. It is only when fusion between two vegetative hyphae of opposite strains of mycelia takes place that the ascogonium develops further.
The nuclei resulting from the hyphal fusions migrate to the ascogonium through the septal perforations. They come to lie by the side of female nuclei in the ascogonium. These pairs of nuclei are called the dikaryons.
They do not fuse. Some mycologists are in favour of their complete fusion in the ascogonium to form diploid nuclei. This assumption is fiercely criticised by the modem mycologists. There seems to be no significance of double fusion and double reduction.
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After the formation of the dikaryons the ascogonium buds out ascogenous hyphae (B). The whole structure now becomes surrounded by a protective sheath of vegetative hyphae.
A pair of nuclei migrates into each ascogenous hypha. These nuclei fuse in the ascus mother cell to form a synkaryon (Fig. 12.16B).
The synkaryon is diploid. After three nuclear divisions of the synkaryon eight haploid nuclei are formed (Fig.12.17).
These nuclei by further changes become ascospores. Each ascospore on falling on a suitable substratum germinates to give rise to a fresh mycelium.
Coprobia (Humaria) rutilans develops no sex organs. The entire sexual apparatus is absent. The sexual process is extremely simplified. Sexual fusion takes place between any two vegetative cells of the hyphae of opposite strains.
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The nuclei of one of the cells migrate into other. There they come to lie in pairs with the nuclei of that cell and form dikaryons. The cells containing a dikaryon or dikaryons bud out ascogenous hyphae.
The subsequent stages of development resulting in the formation of apothecia are the same as in Humaria granulatus.
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