Observations on the Life Stages of Sphaerothecum destruens n. g., n. sp., a Mesomycetozoean Fish Pathogen Formally Referred to as the Rosette Agent

摘要: The rosette agent is an obligate intracellular parasite that causes morbidity and mortality in salmonid fish. In laboratory cultures, the spore stage (2-6 microm diam.) replicates a cell line by sequential asexual division, giving rise to daughter cells. If infected cultures are transferred distilled water, undergoes internal division give at least 5 cells each of which develops into uniflagellated zoospore with body approximately 2 flagellum 10 long. Zoosporulation does not occur culture medium alone, artificial seawater, or phosphate-buffered saline. This currently classified as member Class Mesomycetozoea (formerly Ichthyosporea) based on phylogenetic analyses small subunit ribosomal DNA three different isolates from Given these new morphological observations combined available molecular data other mesomycetozoeans, we propose classify Sphaerothecum destruens, n. g., sp. genus has unique features including (1) development stages various organs eliciting host granulomatous response; (2) differentiation mature spores multiple, flagellated zoospores. Taken together, characteristics clearly distinguish it closely related genera Dermocystidium Rhinosporidium.