Corticolous Myxomycetes X: Ultrastructure and Taxonomic Status of Cribraria Minutissima and C. Confusa

ABSTRACT

Until recently, Cribraria minutissima was broadly described as having sporangia with or without a peridial cup (calyculus). The cupless form was recently given the name Cribraria confusa. Study of type specimens, specimens collected from different geographical areas, and scanning electron micrographs of sporangia support recognition of two distinct taxa. Cribraria minutissima is recognized by cupped sporangia, thickened, smooth upper rim of the cup sharply delimiting it from the peridial net, peridial net devoid of dictydine granules, reddish-orange spore mass, and spore ornamentation of obtuse spines. Surface ornamentation of the cup appears as rounded spherules (dictydine or plasmodic granules) shown with SEM, which often collapse, producing concavities. Cribraria confusa differs from C. minutissima in lack of peridial cup, bright yellow spore mass, smaller sporangia, and spores that bear sharply pointed spines and collapse along preformed lines. In some sporangia a basal disk may be present, or when absent, replaced by basal peridial strands. This disk could not be correlated with other characteristics. Cribraria confusa is the smallest known taxon in the genus Cribraria.

Key Words:

• corticolous myxomycetes
• Cribraria minutissima
• Cribraria confusa
• taxonomy
• ultrastructure