Gill organ culture of rainbow trout, Salmo gairdneri Richardson: an experimental model for the study of pathogenicity of Mycoplasma mobile 163 K

. A method has been developed to maintain gills from rainbow trout, Salmo gairdneri Richardson, in vitro. The gill organ cultures were used to examine the cytotoxic capacities of Mycoplasma mobile 163 K, isolated from the gills of a tench, Tinea tinea L. Histological investigations using light and electron microscopy showed that M. mobile causes heavy damage to the gill epithelium characterized by cytoplasmic vacuolization, peripheral orientation of the condensed nuclear chromatin, separation of the epithelial cells from each other and from the basal membrane, desquamation of the epithelial layer, shrinkage of the cytoplasmic net structure, and a swollen and bleb–like appearance of the apical area of the secondary lamella. The gill organ culture appears to be a suitable model to investigate the cell injuring capacity of M. mobile and may also be applicable to the study of the pathogenic properties of other microorganisms or viruses of fish.