[Various characteristics of the evolution of endoparasites]

Evolution of parasite--host systems should be treated as a specific kind of co-evolution. Although its course is in accordance with the general rules of organic world evolution, it has some peculiarities. One of them is retardation or acceleration of endoparasites' phylogenesis, as compared with the hosts' one. The second one is different speed of phylogenetic changes of endoparasites belonging to the same systematic group. These changes can be significantly limited, as well. Phylogenetic changes of Euglenida--intestinal parasites of Copepoda--are considerably limited, even in comparison with the scale of changes of such species which begin their parasitic life by infecting Copepoda eggs.