Taxonomy of a Giant: The Official Classification of Physarum polycephalum

People call your blob a fungus all the time. That label is wrong in modern classification.

Physarum polycephalum sits in the Amoebozoa lineage, not Fungi. The confusion comes from old naming habits and from fruiting structures that look fungal at first glance.

The hierarchy in plain form

A useful practical hierarchy is:

• Domain: Eukaryota
• Clade/Kingdom-level placement: Amoebozoa
• Class-level group: Myxogastria (commonly called myxomycetes)
• Order: Physarales
• Family: Physaraceae
• Genus: Physarum
• Species: Physarum polycephalum

Terminology can vary across teaching sources, but this placement is the stable conceptual map for most readers.

Why fungus confusion persists

Historically, slime molds were grouped near fungi because they form spore-bearing fruiting bodies. But behavior and cell biology show a different story.

Your blob forages by amoeboid movement and engulfing particles, unlike classic fungal nutrient uptake patterns.

Why “protist” appears in explanations

“Protist” is often used as a broad communication bucket for eukaryotes outside animals, plants, and fungi. It is useful for beginners, but less precise than Amoebozoa placement.

For your guides, best practice is:

• Say “amoebozoan slime mold” when possible.
• Use “protist” only as beginner scaffolding.

Practical writing rule for this site

When first introducing the species:

• Use common + scientific form: the yellow slime mold (Physarum polycephalum).
• Add one-line placement: an amoebozoan myxomycete, not a fungus.

This prevents repeated correction later in the same article.

Why taxonomy matters for experiments

Classification is not trivia. It affects what behavior readers expect.

If readers assume fungus, they expect static growth. If they understand amoeboid lineage, they expect active movement, flow-based adaptation, and dynamic path selection.

That framing improves interpretation of maze, feeding, and transport-network experiments.

Related reading: Taxonomy Decoding, Synchronized Nuclei, and Anatomy.