Ultrastructure and 18S rDNA sequence analysis of Wobblia lunata gen. et an. nov., a new heterotrophic flagellate (Stramenopiles, Incertae sedis)

A new heterotrophic flagellate Wobblia lunata gen, et sp. nov, is described . This organism usually attaches to the substratum showing a wobbling motio n, and sometimes glides on the substratum or swims freely in the medium. W. lunata has various features characteristic of the stramenopiles. These inc lude a hairy flagellum with tripartite tubular hairs, a mitochondrion with tubular cristae, arrangement of flagellar apparatus components and a double helix in the flagellar transition zone. W. lunata shares a double helix wi th heterotrophic stramenopiles, including Developayella elegans, oomycetes, hyphochytrids, opalinids and proteromonads, and could be placed in the phy lum Bigyra Cavalier-Smith. However, from 18S rDNA tree analysis, these orga nisms form two distantly-related clades in the stramenopiles, and Wobblia a ppears at the base of the stramenopiles. Evaluation of morphological featur es and comparison of 18S rDNA sequences indicate that W. lunata is a member of the stramenopiles, but it is distinct from any other stramenopiles so f ar described. Its phylogenetic position within the stramenopiles is uncerta in and therefore W. lunata is described as a stramenopile incertae sedis.