Nuclear Dna Content of Myxamoebae and Plasmodia in Six Non‐heterothallic Isolates of a Myxomycete, Didymium Iridis

Abstract

The nuclear DNA content of six non‐heterothallic isolates of the myxomycete Didymium iridis was measured by combining the Feulgen reaction with absorption microspectrophotometry. This allowed us to distinguish between homothallic (sexual) and apogamic (non‐sexual) isolates. Four of the isolates studied, Panamanian 4 and 5, California 1, and Missouri 1 are homothallic. Moreover, the average DNA content of the myxamoebal and plasmodial nuclei (0.32 and 0.61 respectively) does not differ significantly from the calculated haploid and diploid values for heterothallic isolates of D. iridis (0.34 and 0.63). Hence, it is concluded that in each of these isolates the myxamoebae are haploid and the plasmodia diploid. In two of the isolates investigated, Georgia 1 and Hawaii 1, the DNA content of the myxamoebal and plasmodial nuclei did not differ significantly. Therefore, in both of these isolates the plasmodia appear to develop apogamically. In addition the mean DNA values recorded for the Ha‐1 isolate suggest that it is aneuploid.

Phenotypic plasticity in plasmodial slime molds and molecular phylogeny of terrestrial vs. aquatic species

“…Under moist-chamber conditions, the cultivable myxomycetes fructify. Thus, the two features, i.e., morphology and genetics, should be studied in more detail (see Kamono et al 2013 ; Feest 1987 ; Dahl et al 2017 ; Therrien et al 1977 ; Stephenson et al 2008 ).…”

Genetic Structure of Two Protist Species (Myxogastria, Amoebozoa) Suggests Asexual Reproduction in Sexual Amoebae

“…Such apomictic strains could be haploid or diploid during the entire cycle without any change in the nuclear content and, if diploid, could be homozygous or heterozygous, depending on the state of the sexual ancestors (Table 1). Whether asexual lineages are truly apomictic or have a cryptic sexuality is still unclear, but some lines of evidence point towards true apomixis: isolates usually do not crossbreed [27] and measurements of DNA contents in myxamoebae and plasmodia are identical and appear to be 2n [30]. Cryptic sexuality may thus be only a hypothetical option that could not be ruled out by culture-based studies.…”