Chromosome numbers in representative myxomycetes: a cytogenetic study

Abstract

Myxomycetes are also called plasmodial slime molds, due to one of their characteristic features, the occurrence of the plasmodium. However, most of the distinguishing characters of the five orders currently recognised are based on the morphology of fruiting bodies and spores. Although a few myxomycetes have become widely used model organisms for genetic and cytological studies, complete information relating to the number of chromosomes in haploid cells (n) is lacking thus far. Only two species of the order Physarales have been examined with respect to chromosome numbers. Here, we present a complete data set on the numbers of chromosomes in ten species of myxomycetes that are members of all five orders. Our analysis indicates that n = 21 is the evolutionary ancient chromosome number that occurs in the morphologically simple orders Liceales and Ceratiomyxales. More derived taxa, such as the Physarales, have significantly higher chromosome numbers (n = 30). These data shed light on the phylogenetic relationships within the myxomycetes.