Table 2.

Differentiating features of the globose sporangium-producing Mucorales

Organism nameColony morphologySporangium morphologyApophysis and columella morphology
Rhizopusspp.Floccose; rapidly growingGlobose; variation in size with species and varietyTogether are globose; apophysis is small, may be inconspicuous
Mucor spp.Floccose; rapidly growing; white, yellow, gray or brownGlobose; 15–80 μm wide; deliquescentColumella present, but no apophysis; collars may also be present
Rhizomucor pusillus Floccose mycelium 2–3 μm high; colorless to white, turning grey with ageGlobose with smooth, opaque walls; usually 40–60 μm, may be up to 80 μmPyriform, subglobose, to spherical; 20–45 μm wide
Mortierella wolfii Little aerial mycelium; white, gray, or yellow-grayGlobose and small (15–50 μm); often fails to sporulateLittle or no columella; large colarette left after deliquescence
Absidia corymbifera Floccose; first white, turning brown to greenish brown with ageMay be globose, but more often pyriform, 20–80 μm in diameterApophysis: flask shaped Columella: dome shaped, occupying about 50% of sporangium  
Sporangiospore morphologyRhizoidsSporangiophore morphologyZygosporesOther
Round to oval, often 4–6 μm wide (may be larger); ridgedAbundant, often well developedPredominantly unbranched; occur above rhizoidal tuftsHeterothallicMost species with good growth at 37°C
Smooth walled; oval to round; most 3–5 μm, some largerAbsentPredominantly branchedHeterothallic; chlamydoconidia may be presentRarely grows above 37°C
Smooth walled, globose to broadly ellipsoidal; 3–5 μmPrimitive; rareExtensively and irregularly branched; more typically monopodial; occur between rhizoidal tuftsHeterothallic; round to oval with warts; red, brown, or black; 45–70 μm wideGrowth from 20 to 60°C; assimilates sucrose, glycine, phenylalanine, and β-alanine
Cylindrical or kidney shaped, 6–10 by 3–5 μmPrimitiveShort and tapered, 80–250 μm; occur above rhizoidal tuftsZygospores not seen; chlamydoconidia 35 μm; ameboid appendagesGood growth at >40°C; no growth at >48°C
Round to oval, 2–3 by 3–5 μmPrimitive; rareTall, 450 μm long, arising from stolon; branched, in whorls; occur between rhizoidal tuftsHeterothallic; globose to flattened, rough walled, brown, 50–80 μm wide; 1–5 equatorial ridgesOptimal growth at 37°C; maximum temperature of growth, 45–52°C