parasexuality

Parasexuality is a form of reproduction that results in the recombination of genes from different individuals but does not involve meiosis or the formation of a zygote through fertilization. This process is observed in some fungi, where it involves genetic exchange without the typical sexual reproduction stages.12

In fungi, sexual reproduction typically involves the fusion of two nuclei from sex cells (gametes) to form a zygote, followed by meiosis to restore the haploid number of chromosomes. Parasexuality bypasses these specific steps, instead characterized by heterokaryosis, where a mycelium contains nuclei of different genetic compositions side-by-side.2

While protozoans primarily reproduce asexually, some can undergo sexual reproduction to enhance genetic variation, especially under adverse conditions. Parasitic protozoans often reproduce in large numbers through complex life cycles involving asexual division (schizogony) and sometimes sexual phases. Parthenogenesis, a related concept, is the development of an egg without fertilization, which can be considered an incomplete form of sexual reproduction.34