Euglenids are an important group of free-living phototrophic, osmotrophic, or phagotrophic protists, with most of the phylogenetic diversity represented by phagotrophs. One major subgroup of phagotrophs is the petalomonads: rigid, often relatively small cells with few pellicle strips (usually 4-8). They have been proposed to be sisters to other euglenids, a pivotal evolutionary position supported by multigene phylogenies. Most described petalomonads are assigned to either Petalomonas or Notosolenus; however, neither is monophyletic, and existing genera clearly do not reflect phylogenetic diversity within petalomonads. We report 14 Petalomonas or Notosolenus-like isolates and characterize them using light microscopy, scanning electron microscopy (for most), and SSU rDNA phylogenetics. Most isolates branch in/with three of the five known major clades within petalomonads; however, a new major clade is revealed that houses an isolate identified as Petalomonas poosilla, plus five freshwater Notosolenus isolates, including the type species Notosolenus apocamptus. Overall, we report five new species, plus five new combinations that transfer Notosolenus-like species assigned to other clades to two new genera, Tonotosolenus and Unotosolenus. Over half of the isolates are monoprotistan cultures, markedly increasing the availability of tractable petalomonads for examining euglenid biology in a comparative evolutionary framework.
Lee et al. (Sun,) studied this question.