Lighting lantern above Psalteriomonadidae: Unveiling novel diversity within the genus Psalteriomonas (Discoba: Heterolobosea).

Psalteriomonadidae are a small family of anaerobic free-living protists belonging to Heterolobosea, Discoba. We cultured 74 new strains of mostly amoeboid Psalteriomonadidae obtained from mainly freshwater habitats and sequenced their 18S rRNA gene. Based on the phylogenetic analysis and genetic distances, we report multiple novel species, four of which we formally describe based on the light-microscopic morphology (Psalteriomonas minuta, P. australis, P. fimbriata, and P. parva). We also examined the ultrastructure of two Psalteriomonas species using transmission electron microscopy. We transfer Sawyeria marylandensis into the genus Psalteriomonas and synonymize Sawyeria with Psalteriomonas. In addition, we studied the flagellate stage of P. marylandensis comb. nov. for the first time, using light and scanning electron microscopy.

Free-living Trichomonads are Unexpectedly Diverse.

The vast majority of the more than 450 described species of Parabasalia are intestinal symbionts or parasites of animals. This endobiotic life-history is presumably ancestral although the root of Parabasalia still needs to be robustly established. The half-dozen putatively free-living species thus far described are likely independently derived from endobiotic ancestors and represent the most neglected ecological group of parabasalids. Thus, we isolated and cultivated 45 free-living strains of Parabasalia obtained from a wide variety of anoxic sediments to conduct detailed morphological and SSU rRNA gene phylogenetic analyses. Sixteen species of trichomonads were recovered. Among them, we described seven new species, three new genera, two new families, and one new order. Most of the newly described species were more or less closely related to members of already described genera. However, we uncovered a new deep-branching lineage without affinity to any currently known group of Parabasalia. The newly discovered free-living parabasalids will be key taxa in comparative analyses aimed at rooting the entire lineage and deciphering the evolutionary innovations involved in transitioning between endobiotic and free-living habitats.