Physiological Variation in Strains of Aphanomyces astaci

Abstract
Physiological variation was found both between and within strains of the crayfish plague fungus, Aphanomyces astaci, in culture.The loss of capacity to produce spores was irreversible while losses of motility and virulence to the crayfish were reversible changes. From the tests with motility it was concluded that mutations of hidden or de novo type readily appear in the phenotype of this fungus which belongs to a taxonomic group that is considered genetically very conservative.The authors gratefully acknowledge the assistance of Mrs. Anita Grandin. This research was supported by grants from the Swedish Natural Science Research Council and the Fishery Board of Sweden.