Morphology and development of rumen fungi: Neocallimastix sp., Piromyces communis, and Orpinomyces bovis gen.nov., sp.nov

Developmental stages and morphological variation are described for three species of fungi from the rumen of a Holstein steer. Neocallimastix sp. is monocentric and has endogenous, rarely exogenous, sporangial development. Piromyces communis is monocentric, rarely polycentric, and has both endogenous sporangium development and exogenous sporangia on sporangiophores. Orpinomyces bovis is described for a polycentric fungus with terminal and intercalary sporangiophore complexes that develop from the rhizomycelium, and polyflagellate zoospores. The advantages and limitations of the light microscope and the enigmatic problem of classification of diverse and polymorphic rumen fungi are discussed.