THE ORIGIN OF THE TRYPANOSOMATIDS

Morphological analysis of the evolutionary changes of the cell organiz ation of the Kinetoplastida had shown clear relationship between bifla gellate kinetoplastides on the one hand and trypanosomes from lower ve rtebrates on the other hand. The new hypothesis of the origin of the t rypanosomatides is proposed. From our point of view trypanosomes were derived from Criptobia inhabiting the blood of the freshwater fish. In the process of its evolution the trypanosomatides were loosing recurr ent flagellum and all structures that were associated with them: two k inetosomal rootlets and ventral subpellicular microtubules. On the oth er hand trypanosomatides preserved some ancestral structures such as d orsal rootlet of kinetosom of the anterior flagellum and cytostom-cyto pharyngal complex. The discoidal nucleoid of the kinetoplast and the r ing subpellicular (dorsal) microtubules is the new found feature in th e organization of the Trypanosomatidae.