Oospore

An oospore is a thick-walled sexual spore that develops from a fertilized oosphere in some algae, fungi, and oomycetes.^[1] They are believed to have evolved either through the fusion of two species or the chemically induced stimulation of mycelia, leading to oospore formation.^[2]

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In Oomycetes, oospores can also result from asexual reproduction, by apomixis. These haploid, non-motile spores are the site of meiosis and karyogamy in oomycetes.^[3]

A dormant oospore, when observed under an electron microscope, has led researchers to draw conclusion that there is only a single central globule with other storage bodies surrounding it.^[4]