Diplonema is a genus of excavates belonging to the class Diplonemea. It is a free-living, heterotrophic flagellate found primarily in marine environments. Diplonema are characterized by their distinctive morphology, including two flagella, one forward-facing and one recurrent, and a prominent feeding groove.
As excavates, Diplonema possess defining characteristics of this supergroup, including a feeding groove used for the phagotrophic uptake of nutrients. Specifically, they ingest bacteria and other small particles. The cellular structure includes a complex cytoskeleton and modified mitochondria.
The phylogenetic position of Diplonema within the Excavata is important for understanding the evolution of eukaryotic cells and their metabolic diversity. The genus has been studied using molecular phylogenetics, contributing to a better understanding of its relationships to other excavates and eukaryotes generally.