| The developmental and morphological variations of selected taxa of rumen zoosporic fungi isolated from cattle in Georgia was studied with light and fluorescence microscopy. Isolates of rumen fungi were also obtained from the feces of an individual cow and correlated with isolates from the rumen of the same cow.;Three monocentric and two polycentric fungi were isolated from the rumen, freshly voided, moist and dry feces. Rumen isolates were morphologically similar to the fecal isolates of the same cow. The monocentric isolates were Piromyces sp., Caecomyces communis and Neocallimastix sp. and the polycentric isolates were Orpinomyces sp., types PC2 and PC3. Piromyces sp. had uniflagellate zoospores that developed endogenously into a thallus consisting of a sporangium and branched rhizoids. The zoospores of both types of Orpinomyces sp. were multiflagellate. Type PC2 produced laterally-borne, stalked zoosporangia and melanized sporangia with one or more globose appendages on the sporangia, while type PC3 formed a catenulate rhizomycelium with sessile zoosporangia and melanized sporangia.;The posteriorly uniflagellate zoospores of Caecomyces communis developed to form either a thallus consisting of one or more sporangia attached to a large, vacuolate vegetative cell, or the vegetative stage was myceloid. The vegetative cell or mycelium was nucleate. Outgrowths which enlarged to form thick filaments were produced by the vegetative cell. In the myceloid form, at maturity, sporangia were formed at the tips of the filaments.;Encysted zoospores of Neocallimastix sp. germinated and developed endogenously to form a chytrid-like thallus made up of intramatrical, branched rhizoids and an extramatrical, sessile or stalked zoosporangium. Mature zoosporangia varied in shape and zoospores were fully formed within the zoosporangium before release through an apical pore. Second generation zoospores encysted near the original sporangium and often developed exogenously into an elongate thallus made up of a sporangium, a sporangial stalk, a cyst and rhizoids. There was a shift from the development of zoosporangia to the formation of melanized resistant sporangia (RS) on branched thalli in older ($>$36 h) cultures. During RS formation, the elongate thallus often branched monopodially near the tip. Nuclei and cytoplasm migrated into the enlarged tip and a septum was formed before the RS became melanized. The DNA content of mature RS was twice the highest level in the zoosporangium which indicated that there was a diploidization during RS formation. Neocallimastix frontalis strains PN1 and PN2 and N. patriciarum were grown under the same conditions as our isolate, and they were morphologically and developmentally similar to each other and to our isolate. |
