Most diplomonads are double cells: they have two nuclei, each with four associated flagella, arranged symmetrically about the body's main axis.However, researchers found G. duodenalis to have a core set of genes that function in meiosis and that are widely present among sexual eukaryotes.Furthermore, Cooper et al.[6] found direct evidence in Giardia duodenalis for infrequent meiotic recombination, indicative of sexual reproduction between individuals.Giardia duodenalis is divided into eight assemblages based on host specificities and genetic divergence of marker genes.They suggested that the assemblages are genetically isolated lineages, and thus could be viewed as separated Giardia species.