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Walker & Sanders (1986) |
| Etymology: | Latin, "shielded" Greek, "spore" |
| Description: | Spores with or without ornamentations. Sexual spores have not been reported. Subcellular organization of spores consists of a bilayered spore wall and one to three flexible inner walls. Groups of species share the same inner wall structure (one, two, or three inner flexible walls with layers that differ in thickness, degree of plasticity, and reaction to Melzer's reagent). Species-level differences occur in phenotypic variation in layers of the spore wall (ornamentations of the outer layer, color of the laminate layer, etc.). Germ tubes arise from a persistant, plate-like germination shield that is always assiociated with the innermost flexible wall. Thin-walled auxiliary cells with smooth to knobby surfaces, are produced on hyphae in the soil near the root surface. |
| Type species: | S. calospora (Nicol. & Gerd.) Walker & Sanders |
Early stages in spore development mirror those in the sister genus, Gigaspora. Spores develop blastically from a hyphal tip, which swells and becomes the "sporogenous cell". After the sporogenous cell reaches it's full size (usually about 25-50 µm in most species), the spore begins to develop at the tip. The outer layer and the laminate layer develop simultaneously, and often cannot be distinguished in juvenile spores without the assistance of Melzer's reagent. The laminae then thicken and the outer ornamentations develop (if present in the species). Inner walls develop and the last stage is the formation of the germination shield.
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