Studies on cultured and gill-attached Paramoeba sp. (Gymnamoebae: Paramoebidae) and the cytopathology of paramoebic gill disease in Atlantic salmon, Salmo salar L., from Tasmania |
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| Authors: | F R ROUBAL R J G LESTER C K FOSTER |
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| Institution: | Department of Parasitology, University of Queensland, Brisbane, Queensland, Australia;SALTAS, Dover, Tasmania, Australia |
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| Abstract: | Abstract. The normally free-living amoeba Paramoeba sp. is associated with epithelial hyperplasia on the gills of Atlantic salmon, Salmo salar L., in Tasmania. Gill-attached paramoebae were significantly larger than cultured ones. Unlike cultured paramoebae, gill-attached ones had small electron-dense, cytoplasmic deposits and small surface projections at the host-parasite interface. Examination of sequential samples of Tasmanian salmon gills from spring to summer indicated that pathological changes in the gill filaments were associated only with the presence of Paramoeba ; the parasite was also associated with necrosis of surface epithelial cells, and cytoplasmic processes passed into and between surface cells of hyperplastic gill epithelium. The evidence points to the paramoebae as primary opportunistic pathogens causing mechanical and possibly chemical damage. Based on size and ultrastructure, the Paramoeba sp. most closely resembles P. pemaquidensis Page. |
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