Screening of the entire genome of the pea aphid, Acyrthosiphon pisum, detected 15 genes for putative dynamin superfamily proteins – self-assembling large GTPases that are involved in the fission and fusion of membranes. In addition to a single gene each for Dyn, Drp1, and Opa1, orthologues that are common in Metazoa, 12 genes encoding a novel type of dynamin were found. Phylogenetic analyses showed that these novel-class genes are monophyletic. Quantitative reverse transcription-PCR demonstrated that expressions of four novel-class dynamin genes are highly up-regulated in the midgut, through which aphids take in phloem-sap diets and plant viruses. As this type of dynamin is absent from all other fully sequenced organisms, they may function in processes unique to aphids.