Zygospore

A zygospore of "zygo- , Greek = yoke and spora = seed" is a diploid reproductive stage in the life cycle of various fungi. Zygospores are formed by nuclear fusion of haploid cells. Until 2007, zygomycetes or zygomycota formed a division within the fungal kingdom. They are named after the yoke-like structures that occur during sexual reproduction.

Zygospores are formed by recombination of the genetic information of two organisms. However, the two individuals must belong to a different mating type. This cannot usually be determined externally. It is therefore not called male or female, but only a plus or minus type. This form of reproduction is called heterothallie.

The fusion process is initiated by pheromones (messenger substances). Here yoke-like bridges are formed between the 2 hyphae. For this purpose, special structures, the gametangia, grow out of both cell filaments and touch each other. It comes to a swelling of the contact surfaces. As a consequence, the cytoplasmic partition wall dissolves at this point. This leads to plasmogamy, a fusion of the cytoplasmic parts of the gametangia. The cell nuclei initially remain separated from each other. Within the zygospore a nuclear fusion (karyogamy) then takes place between two nuclei. A structure characterized by two complete sets of chromosomes (diploid state) is formed in the short term. This state lasts only briefly in the life cycle of the yoke fungi. If the environmental situation is favourable, the zygospore germinates. Meiosis occurs and haploid vegetative cells are released.

Fungi that form zygospores are called zygomycetes or zygomycota or zygomycota fungi. Until 2007 they formed a separate section within the classifications of fungi.