LOW GENETIC DIVERSITY IN WILLAERTIA-MAGNA FROM WIDE GEOGRAPHICAL SOURCES, AND CHARACTERIZATION OF WILLAERTIA-MINOR N-SP (HETEROLOBOSEA, VAHLKAMPFIDAE)

Twelve isolates assigned to Willaertia magna by morphological and physiological criteria, including the type material, were characterised at 23 enzyme-encoding loci. Isolates from Australia, Bangladesh, Belgium, England, France, Indonesia, Japan, Korea, Madagascar and Papua New Guinea showed fixed alleles at 18 loci and polymorphism at Acp, Lap, Me, 6Pgd and Pgm 1. The maximum difference in pairwise comparisons was 8.7%, consistent with intra-specific variation in the related genus Naegleria. An additional isolate, assigned to Willaertia by features of its flagellate and cyst stages, represents a new species. Willaertia minor n. sp. shares alleles with W. magna at only three loci, has a maximum growth temperature of 38-degrees-C and is significantly smaller in all stages than W. magna. Flagellates appear to divide only once and fail to replace the lost flagella, producing biflagellate daughter cells. Cysts and trophozoites are more readily mistaken for Naegleria, but lack perinuclear granules, as do the mature cysts of W. magna.