Six strains of amoebae belonging to two species, vizAcunthamoeba culbertsoni andAcanthamoeba rhysodes, were isolated during the 3 prominent seasonal periods of premonsoon, monsoon and postmonsoon from the south of Sagar Island facing Bay of Bengal (21°56′ to 21°88′ N and 88°08′ to 88°16′E). The actual sampling sites were the lowest low tide belt areas. They were co-cultured in pairs, for respective seasonal periods, in 20‰ saline distilled water agar medium with their habitat associated microbiota as food. Dominance of all the seasonal isolates ofAcanthamoeba culbertsoni over the corresponding strains ofAcanthamoeba rhysodes arising out of competitive growth has been observed. Thus in laboratory maintained cultural conditions, strains ofAcanthamoeba culbertsoni show remarkable adaptive superiority over those ofAcanthamoeba rhysodes.