ascosporer

An ascospore is a sexual spore formed inside an ascus, the sac-like cell unique to the fungi of the phylum Ascomycota. In most species, asci are contained within fruiting bodies called ascocarps, and each ascus typically produces eight ascospores through meiosis followed by a post-meiotic mitotic division. The spores are haploid and carry genetic material recombined from the parent mycelia.

Formation begins with plasmogamy between compatible hyphae, followed by karyogamy within the ascus. Meiosis then produces haploid nuclei, often followed by an additional mitotic division, yielding the characteristic eight spores in many species. Ascospores are released when the ascus or ascocarp ruptures and can disperse through wind, water, or animals, germinating to form new haploid mycelium under favorable conditions.

Ascospores exhibit considerable diversity in size, shape, color, and surface ornamentation, reflecting adaptations to different environments. They serve as key taxonomic characters in identifying Ascomycota. Ascocarps come in various forms, including apothecia (open, cup-like), perithecia (flask-shaped with a pore), and cleistothecia (fully enclosed). In some yeasts, ascospores form during sexual cycles under nutrient limitation, with species such as Saccharomyces and Neurospora commonly studied as model organisms for fungal genetics and life cycles.