Dictyostelium Minutum, A Second New Species of Slime Mold from Decaying Forest Leaves

SUMMARY

A new species of Dictyostelium isolated from forest litter is described. Because of the diminutive character of its sorocarps the name D. minutum is proposed.

In the size and pattern of its spores and in the behavior of its vegetative myxamoebae in culture, the species closely resembles D. mucoroides. It is distinguished from this species primarily by the conspicuously smaller dimensions of its pseudoplasmodia and sorocarps and secondarily by the pattern of its completed fructifications. In thin cultures under optimum environmental conditions, radiate pseudoplasmodia appear, but they are not formed as consistently as in the larger species. Mature sorocarps are diminutive and unsubstantial. Typically they consist of short, thin, tapering sorophores bearing comparatively large, colorless to milk-white sori. Normally the sorophore consists of a single tier of cells throughout the greater portion of its length, the individual cells varying in shape from flattened and discoid toward the base to elongate and tube-like at the apex. Branched sorocarps are more common than in any other species of Dictyostelium.