Variation in the Cellular Slime Mold Acrasis rosea*

Abstract

A number of isolates of the cellular slime mold, Acrasis rosea, differed from each other in the range of microorganisms on which they could grow and fruit. In a test for the possible occurrence of sexual reproduction and genetic recombination, two of the most widely divergent of these physiological races were studied further. Mixed colonies were obtained in agar plate cultures of Rhodotorula mucilaginosa, a yeast utilized by both. When spores from mature fruiting bodies or amoebae migrating out from the mixed colonies were isolated singly, regrown on Rhodotorula, and tested on a critical spectrum of food microorganisms, about 3‐4% proved to be distinct from the original two strains. Although some of these new types remained stable for several transfers, they eventually reverted to one or both of the parental types. The possibilities of explaining the neotypes on the basis of diploidy, heterokaryosis, or mixed cytoplasmic effects are discussed. The occurrence of cell anastomoses and occasional binucleate cells favors the latter two possibilities.

Exploitation of Other Social Amoebae by Dictyostelium caveatum

“…It was not possible to test all known species, but we chose at least one representative species of each group defined by a phylogenetic tree constructed by Schaap and colleagues [5]. We also tested the effect of D. caveatum on Acrasis rosea , which, though it is amoeboid and has an aggregative developmental cycle, is unrelated to the Dictyostelia [11], [12]. Its amoebae are also ingested by D. caveatum (not shown).…”

Diversity of Heterolobosea

“…Although the sexual reproduction of several heterolobosean species has been discussed (e.g., Bunting, 1926;Droop, 1962;Fritz-Laylin et al 2010;Olive et al, 1961;Olive, 1963;Pernin et al, 1992), no direct evidence has been found and the nature of the putative sexual processes remains unclear. Some authors hypothesize that the amoeba is the diploid stage whereas the flagellate is haploid and represents the gamete (Droop, 1962;Fulton, 1993).…”

A Morphologically Simple Species of Acrasis (Heterolobosea, Excavata), Acrasis helenhemmesae n. sp.

“…The new cellular slime mold isolates are clearly in the genus of Acrasis sensu Olive and Stoianovitch (1960). The amoebae of our isolates are morphologically identical to those of A. rosea (Olive and Stoianovitch 1960;Olive et al 1961). Amoebae have a single nucleus with a large centrally located nucleolus.…”

“…Acrasis rosea was originally described to be an extremely plastic organism, in which a single isolate may display a wide variety of complexity in fruiting body morphology once in culture (Olive and Stoianovitch 1960). Later studies on variation in A. rosea increased our recognition of the diversity of the species (Olive, Dutta, and Stoianovitch 1961; Reinhardt 1968, 1975), but these studies may have been handling multiple species, which could now be delimited by modern molecular techniques.…”