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.