Redescription of the protostelid genus Microglomus, its type species and a new variety

Abstract

Following new information obtained by transmission electron microscopy (TEM), the protostelid genus Microglomus (Class Eumycetozoa) and its type species are redescribed. A new variety of its single known species is also described. Instead of there being a few spores within a stalked microsporangium as previously considered, TEM studies show that the stalk of the fruiting body is terminated by a single spore, the wall of which contains spinulose extensions characteristic of the spores of several other protostelids as well as myxomycetes. The mature spore of the type collection, M. paxillum var. paxillum, typically contains four cells that emerge as amoebae with mostly filose pseudopodia at germination. A new variety, M. paxillum var. bicellulare, isolated from dead parts of an orange tree collected in Florida, differs from the type species by typically having 2 nuclei rather than 1 in the rising sporocarp and 2 rather than 4 binucleate cells within the mature spore, although several exceptions are noted. Synaptonemal complexes occur in spore nuclei of both varieties prior to nuclear division.