An amoeba associated with gill disease in turbot, Scophthalmus maximus (L)

An amoeba associated with a severe gill disease affecting farmed turbot, characterized by pronounced hyperplasia of the branchial epithelia and accumulation of mucus between the secondary lamellae, is described for the first time. The amoeba was isolated, cloned and cultured on Bactoagar. Light microscopy showed that trophozoites had a mean length of 12 mu m (range 8-20 mu m), with a nucleus 3-5 mu m in diameter containing a large central nucleolus 1-3 mu m in diameter. Transmission electron microscopy showed that the mitochondria, Golgi bodies, rough endoplasmic reticulum, microfilaments, cytoplasmic microtubules and glycocalyx were similar to those previously reported for the genus Platyamoeba. These and other findings strongly suggest that the amoeba isolated is of the genus Platyamoeba, while its morphometric characteristics suggest that it may represent a new species. This is the first report of a species of the genus Platyamoeba in association with gill disease in turbot.