<em>Collaria arcyrionema</em> is a myxomycete — a plasmodial slime mould — belonging to the class Myxomycetes within the phylum Mycetozoa. Slime moulds of the genus Collaria are not true fungi but are instead classified within the group Amoebozoa, reflecting their distinctive biology that combines amoeba-like feeding behaviour with a complex, multi-stage life cycle. <em>Collaria arcyrionema</em> produces small, stalked sporangia — spore-bearing structures — that are characteristic of the genus, typically forming on decaying organic matter such as dead wood, leaf litter, and damp substrate in forested environments. The species has a reported distribution in Brazil, Norway, and Sweden, with occurrence noted across parts of Europe and South America. Like other myxomycetes, <em>Collaria arcyrionema</em> plays a role in nutrient cycling by consuming bacteria and organic detritus during its plasmodial phase. Detailed biological traits including typical lifespan measures and physical dimensions are poorly documented for this species in available literature.