Parasitic Stramenopila

In the vast and diversified eukaryotic group Stramenopila we can find many different life strategies, one of them being parasitism. There are two groups of stramenopiles containing important parasites of vertebrates: the oomycetes (e.g. Saprolegnia) and the wholly parasitic group Slopalinida+its sister taxon—Blastocystis. The order Slopalinida comprises families Opalinidae and Proteromonadidae. The two families are considered related based on the structure of basal bodies and their appendages and the presence of subpelicular microtubules. However, a robust recognition of phylogenetic affinities of Opalinidae—the peculiar multinucleated intestine commensals of frogs—has been hindered by the absence of reliable molecular data. Up to now, all attempts to sequence opalinid genes failed, as the obtained sequences labeled as Protoopalina intestinalis, Cepedea virguloidea and Opalina ranarum in GenBank apparently originate from a zygomycete contamination. We present the first molecular data for the family Opalinidae—SSU rRNA gene of Protoopalina intestinalis. Our phylogenetic analyses undoubtedly show opalinids as a sister group to Proteromonas within the Stramenopila clade, confirming th