Phylogenetic Placement and Morphological Description of Three Species of Heterotrophic Euglenids (Euglenozoa) From Arizona: Scytomonas flumensis n. sp., Ploeotia protuberantia n. sp., and Hokulea pusilla comb. nov.

Euglenids are microbial flagellates best known for their highly flexible photosynthetic species (e.g., Euglena gracilis), though many heterotrophic groups remain poorly characterized at both molecular and ultrastructural levels. In particular, rigid heterotrophs such as ploeotids and petalomonads are highly diverse, yet most described species were documented only with light microscopy, largely because they are difficult to cultivate. Here, we establish cultures for three new isolates of ploeotids and petalomonads (Hokulea pusilla comb. nov., Ploeotia protuberantia sp. nov., Scytomonas flumensis sp. nov.) and examine them using light microscopy, scanning electron microscopy, and 18S rDNA phylogenetic analyses. These data support the recognition of two new species, Ploeotia protuberantia sp. nov. and Scytomonas flumensis sp. nov., and justify the transfer of Ploeotia pusilla to Hokulea pusilla comb. nov. based on its morphology and its affiliation with Hokulea waialensis in 18S rDNA phylogenies.