Neoparamoeba sp. and other protozoans on the gills of Atlantic salmon Salmo salar smolts in seawater.

Protozoan isolates from the gills of marine-reared Atlantic salmon Salmo salar smolts were cultured, cloned and 8 dominant isolates were studied in detail. The light and electron-microscopical characters of these isolates were examined, and 7 were identified to the generic level. Structure, ultrastructure, a species-specific immunofluorescent antibody test (IFAT), and PCR verified the identity of the Neoparamoeba sp. isolate. Five other genera of amoebae, comprising Platyamoeba, Mayorella, Vexillifera, Flabellula, and Nolandella, a scuticociliate of the genus Paranophrys, and a trypanosomatid (tranosomatid-bodonid incertae sedis) accompanied Neoparamoeba sp. in the gills. The pathogenic potential of the isolated organisms, occurring in conjunction with Neoparamoeba sp. in the gills of cultured Atlantic salmon smolts in Ireland, remains to be investigated.