[Differentiation of Leishmania in culture]

During their cultivation on diphasic medium Leishmania donovani, L. major and L. gymnodactyli pass through the regular differentiation within the promastigote stage of the life cycle that involves a gradual change of the four main morphological forms: 1) extremely basophilic, short, wide, actively dividing cells; 2) lightening longer forms with pointed posterior ends; 3) long, cigar-shaped uniformly light specimens with the clear nucleus in the central or posterior position and distinct karyosome; 4) small narrow nearly non-basophilic cells with a long compact nucleus and a rather large kinetoplast. The latter are similar, on the one hand, to the final stage of Leishmania development in Phlebotomus and, on the other hand, to metacyclic forms of Trypanosoma cruzi infective for the vertebrate host.