Giardia lambila is an intestinal parasite of humans and other mammals. It is a protist known as a diplomonad in the Supergroup Excavata, Subgroup Metamonada. This subgroup is defined by the presence of two nucleii, multiple flagella, and modified mitochondria that are not capable of undergoing the electron transport chain. There members of the Metamonada can grow in anaerobic (lacking oxygen) environments.
Photo: Josef Reischig 2014.