First Molecular Characterization of the Elusive Marine Protist Meteora sporadica

Meteora sporadica is a protist species first described by Hausmann et al. (2002) in deep-sea sediments from the Sporades Basin, Eastern Mediterranean Sea. Due to its unusual morphology and locomotion, very different from those of other high-rank eukaryotic taxa, it was classified as an incertae sedis species. Unfortunately, its morphological characterization was not accompanied by the generation of molecular data, preventing its placement in molecular phylogenetic trees including other protist lineages. Here, we report the observation of protist cells in sediments from a shallow marine lagoon in the Mediterranean Sea with morphological characteristics indistinguishable from those of Meteora sporadica. Given this similarity and the geographical proximity to the type location, we consider that the organism that we observed likely corresponded to the type species, M. sporadica, which seems to be a benthic predator spanning from shallow to deep-sea habitats. We determined the 18S rRNA gene sequence of M. sporadica from micromanipulated cells. Searches in sequence databases did not yield closely related hits, suggesting that Meteora is a rare organism. Phylogenetic analyses did not show any close affinity with other eukaryotic groups, supporting its initial incertae sedis status and suggesting that it may define a new high-rank level eukaryotic lineage.