High-altitude Amazonian eukaryotic shells (Arcellinida, Amoebozoa)

The microbial eukaryote diversity of the Amazonian rainforest remains mostly undescribed, particularly for higher-altitude sites located within indigenous lands that are characterized by very difficult access. We obtained a bryophyte sample during the Brazilian expedition to the Serra do Imeri in 2022, one of the highest elevations in the forest. We preserved part of the sample and examined another part to determine the identity of bryophyte species and to search for Arcellinida shelled amoebae. In this single sample, we found 142 shells distributed across 17 different nominal taxa. We found one shell of a potentially new taxon, similar to representatives of the genus Padaungiella. Here we provide a morphological characterization of the recorded taxa, using both optical and scanning electron microscopy, including morphometrics and morphological descriptions. We conclude with taxonomic remarks and a discussion of morphological variation in the specimens found at Serra do Imeri.