Zygopolaris, A New Genus of Trichomycetes Producing Zygospores with Polar Attachment

Abstract

SUMMARY A new monotypic genus of the fungal order Harpellales (Genistellaceae) has been found in three localities in the United States inhabitating the guts of mayfly nymphs, Ephemerella and Baetis. Mature sporulating thalli of Zygopolaris ephemeridarum may be found protruding from the the anus of the host into the aquatic environment. Released trichospores do not appear to have basal appendages, as do most other Harpellales, but evidence of rudimentary appendage formation has been found in the generative cells. Zygospores are attached at one pole, and resemble those of Carouxella (Harpellaceae). The similarities of the two genera and two families are discussed, as well as the four types of zygospores recognized in the Harpellales. Zygopolaris, a new genus of Trichomycetes growing in the hindgut of mayfly nymphs in flowing streams, has been found in several different areas in western United States, thus indicating that it may be widespread. The genus is monotypic, like the majority of Harpellales genera (Manier and Lichtwardt, 1968; Lichtwardt, 1972). Its distinctive characteristics are attachment of zygospores at one pole, the lack of welldefined trichospore appendages, and projection of thalli from the host anus. All attempts to culture the species, Zygopolaris ephemeridarum, were unsuccessful, and all observations were made from material dissected from the living hosts. The majority of measurements and photographs were taken from distilled water mounts prior to their infiltration with lactophenol containing cotton blue.