Notes on the Morphology and Taxonomy of Micromyces (Synchytriaceae, Chytridiomycota), with special attention to M. longispinosus, M. grandis, M. furcatus and M. ovalis

摘要

Traditionally, family Synchytriaceae has been placed in order Chytridiales, phylumChytridiomycota. Within the family, though, the taxonomic situation has been less clear. This family hasbeen considered to contain only a single genus (Synchytrium), or as many as four genera: Synchytrium,Micromyces, Micromycopsis and Endodesmidium (cf. Sparrow, 1943, 1960; Karling, 1977)--eitherapproach perhaps tenable. However, since the ‘separate genera’ appear distinct, and until contravened bymolecular evidence, we recognize them here. Karling (1964), while adopting the single-genus approach(recognizing only Synchytrium, with a number of subgenera), nonetheless provided a helpful compilationof information. However, taxonomic attention is still needed in the family. We review taxa of the aquaticgenus Micromyces (endoparasites of conjugate algae, i.e., Zygnemataceae). Sparrow’s (1960) key tospecies of Micromyces has stood well until the present. But, since Sparrow (1960) did not recognizeMicromycopsis (including its species in Micromyces), and since we herein recognize Micromycopsis,adjustments to the Micromyces key were necessary. Also, certain potential species of Micromyces thatwere not included in Sparrow’s taxonomic key (i.e., M. grandis Miller, 1955 and M. “furcata” Rieth,1962) required evaluation. We determine M. grandis to be a large variant of M. longispinosus Couch(1937). Micromyces “furcata” Rieth (1962), subsequently accounted for mainly in listings ofChytridiomycete names, is morphologically distinct, and is added to species in our key. The epithet“furcata” (Rieth, 1962) should be “furcatus,” viz. M. furcatus (Index Fungorum). Micromyces ovalis(Rieth, 1950) is nomenclaturally invalid (lacking the Latin diagnosis required at the time); an Englishdiagnosis (see present rules of nomenclature) is here provided. In addition to various points ofnomenclatural clarification, we hope that our observations of living material of M. longispinosus will addto morphological understanding of this species. Future molecular studies should inform as to relationshipsamong Micromyces species, and how many genera of Synchytriaceae should be recognized. Publishedon-line www.phytologia.org Phytologia 100(1): 51-61 (Mar 16, 2018). ISSN 030319430.