Table 10.

Differentiating features of Rhizomucor pusillus and Rhizomucor miehei

Organism nameColony morphologySporangium morphologyColumella morphologySporangiospore morphology
Rhizomucor pusillus Floccose mycelium 2–3 μm high; colorless to white, becoming grey with ageGlobose with smooth, opaque walls, usually 40–60 μm, may be up to 80 μm  Pyriform, subglobose, or spherical; 20–45 μm wideSmooth walled, globose to broadly ellipsoidal, 3–5 μm
Rhizomucor miehei Low-growing colonies, darker thanR. pusillus; dirty gray to brown gray  Globose with spiny walls, 50–60 μmPyriform to subglobose, rarely over 30 μm wideSmooth walled, globose to broadly ellipsoidal, 3–5 μm
RhizoidsSporangiophore morphologyZygosporesOther
Primitive; rareExtensively and irregularly branched; more typically monopodial; occur between rhizoidal tuftsHeterothallic; zygospore formation best from 30 to 40°C; round to oval with stellate warts, red, brown or black; 45–70 μm wideGrowth from 20 to 60°C; assimilates sucrose, glycine, phenylalanine, and β-alanine
Primitive; rareBranched sympodially, and more loosely than R. pusillus; occur between rhizoidal tuftsHomothallic; round to oval zygospores with stellate warts, red, brown or black; 50 μm wideSlow growth at 25–30°C with growth up to 58°C; does not assimilate sucrose, glycine, phenylalanine, or β-alanine