A protozoan family of hemoflagellates (order Kinetoplastida, class Zoomastigophorea, subphylum Mastigophora); asexual blood and/or tissue parasites of leeches, insects, and vertebrates and sap inhabitants of plants, characterized by a rounded or elongate form, a single nucleus, elongate mitochondrion (its position in relation to the nucleus is a characteristic of each genus), and an anteriorly directed single flagellum (in some genera, it borders an undulating membrane). Trypanosomatidae includes the genera Crithidia, Herpetomonas, Leptomonas, and Blastocrithidia, all of which are monogenetic and found in insects, and Phytomonas (found in plants), Endotrypanum, Leishmania, and Trypanosoma, all of which are digenetic; Leishmania and Trypanosoma include important pathogens of humans and animals. Many trypanosomes pass through developmental or life cycle stages similar to the body forms characteristic of the genera; these forms include amastigote, choanomastigote, opisthomastigote, promastigote, epimastigote, and trypomastigote.