Külgetungi

Külgetungi is a fictional term used in speculative biology and world-building to describe a proposed class of flexible symbiotic organisms that blend fungal and photosynthetic traits. In imagined taxonomies, külgetungi form thallus-like bodies with a hyphal network interwoven with photosynthetic endosymbionts, such as algae or bacteria. They are portrayed as modular, allowing parts of the organism to function independently in response to environmental changes.

In terms of biology, külgetungi are described as having a layered structure where fungal-like filaments provide shelter and nutrient access, while the phototrophic cells harvest light to supply energy. Their life cycle is depicted as capable of switching between saprotrophic and phototrophic modes, enabling persistence on diverse substrates and through periods of drought or low light. Reproduction in the narratives often involves spores that carry endosymbionts, promoting rapid colonization and potential vertical transmission.

Ecologically, külgetungi are imagined as pioneer organisms in disturbed or nutrient-poor environments—on bare rock, decaying wood, and exposed soils—where their dual metabolism accelerates stabilization of substrates and soil formation. Researchers within these stories examine signaling between fungal and phototrophic components, exploring how nutrient exchange is regulated and how mutualism evolves under shifting conditions.

Cultural and educational use of the concept centers on discussions of symbiosis, ecological resilience, and the boundaries between kingdoms in biology. See also: lichens, mycorrhiza, endosymbiosis.