Small subunit ribosomal DNA phylogeny of microsporidia with particular reference to genera that infect fish

Molecular data have proved useful in the study of microsporidia phylogeny. Previous studies have shown that there are several important differences be tween phylogenies based on rRNA and morphological data. Ln the present stud y, small subunit (SSU) rDNA sequences were obtained from 7 different fish-i nfecting microsporidia from 4 different genera (Glugea Thelohan, 1891, Loma Morrison and Sprague, 1981, Pleistophora Gurley, 1893, and Spraguea Weisse nberg, 1976). The lengths of the SSU rDNA genes in these species were betwe en 1,332 and 1,343 base pairs. Phylogenetic analysis was performed using pa rsimony, maximum likelihood, and Kimura 2-parameter with neighbor joining. The analyses revealed that the microsporidia could be divided into 3 major groups. With the exception of Nucleospora salmonis Hedrick, Groff, and Baxa , 1991, all the microsporidia infecting fishes occurred in the same group. The analysis showed that Pleistophora mirandellae Vaney and Conte, 1901 and Pleistophora aguillarum Hoshina, 1951 are not species of Pleistophora. Fur thermore, the analysis showed that Loma is not a member of Glugeidae Theloh an, 1892.