Phylogenomic Placement and Morphological Description of a Novel Phagotrophic Euglenid From Hawaii: Hokulea waialensis n. gen. et sp.

Abstract

Euglenids are a diverse group of flagellated protists that include phagotrophic, osmotrophic, and phototrophic lineages. Understanding the phylogenetic relationships of phagotrophic euglenids is crucial in understanding euglenid evolution. Yet many relationships within euglenids remain unclear, and further resolution requires extensive sampling, particularly from the deep-branching, paraphyletic group known as “ploeotids”. Improved resolution of evolutionary relationships among ploeotid taxa is necessary to elucidate the origin and diversification of complex ultrastructural traits (e.g., pellicle and feeding apparatus). Here, we isolated, cultivated and characterized a novel freshwater “ploeotid” species named Hokulea waialensis n. gen. et sp. using light and scanning electron microscopy, single-cell sequencing, and phylogenomic analyses. This new species is relatively small (~10 μm long) compared to related euglenids and shares several morphological traits with related species of Alistosa. Both single and multigene phylogenetic reconstructions from single amplified genome data show that Hokulea waialensis n. gen. et sp. is closely related to several environmental small subunit ribosomal DNA (SSU rDNA) sequences, and more broadly to Lentomonas and Decastava.