yksisoluisetsien

Yksisoluisetsien is a term used in Finnish-language speculative biology to denote an informal grouping of unicellular fungi and related unicellular eukaryotes. The name comes from yksisoluiset (unicellular) and sienet (fungi) and is used mainly outside formal taxonomy.

Members are described as lacking true multicellular mycelia, or possessing only transient filament-like structures. They are envisioned as single cells or simple colonies with diverse metabolisms, including fermentation and osmotrophy. Traits include a chitin- and glucan-rich cell wall, small to moderate cell size, and reproduction by budding, fission, or spores in some lineages.

Ecologically, they are imagined in soils, plant surfaces, animal guts, and fermented environments, where they act as decomposers, symbionts, or opportunistic pathogens. Yeasts such as Saccharomyces cerevisiae and Candida species are often cited as familiar representatives, though they belong to established fungal lineages rather than a single formal group.

Scholars differ on the value of recognizing yksisoluisetsien. Proponents argue the label highlights shared unicellular traits across fungal lineages; critics warn it can blur phylogeny. Today the concept remains unofficial and mainly appears in speculative or educational contexts; formal recognition would require clear phylogenetic criteria and consensus.