Molecular evidence that Reticulomyxa filosa is a freshwater naked Foraminifer

Reticulomyxa filosa is a freshwater protist possessing fine granular, branc hing and anastomosing pseudopodia and there fore traditionally placed in th e class Granuloreticulosea, order Athalamida, as a sister group to the orde r Foraminiferida. Recent studies have revealed remarkable similarities in p seudopodial motility and ultrastructure between R. filosa and foraminifera (e.g. Allogromia laticollaris), prompting us to conduct a molecular phyloge netic analysis of these seemingly disparate organisms. We sequenced the com plete small-subunit of the ribosomal DNA of the cultured strain of R. filos a and compared it to the corresponding sequences of other protists includin g 12 species of foraminifera. We also sequenced and analyzed the actin codi ng genes from R, filosa and two species of foraminifera, Allogromia sp. and Ammonia sp. The analysis of both data sets clearly shows that R. filosa br anches within the clade of foraminifera, suggesting that R. filosa is in fa ct a freshwater naked foraminiferan.