The formation of primary and secondary lysosomes in Balantidium coli, Ciliata.

Trophozoites, vegetative forms of Balantidum coli isolated from pigs affected by acute and asymptomatic balantidiasis were studied. Lysosomes and food vacuoles were revealed by cytochemical detection of lysosomal marker, acid phosphatase. The cytoplasm of all the B. coli trophozoites examined was found to contain numerous structures which differed widely in shape, size and location in the cells. One of them was located among the rough endoplasmic reticulum membranes and another one in the vicinity of endosomes. Those structures were regarded as the primary lysosomes. The two types of vesicular structures most probably represent two stages of the primary lysosome formation. Trophozoites were also found to contain secondary lysosomes which are formed by fusion of several primary lysosomes with phagosomes. The ultrathin sections of B. coli trohozoites showed the presence of two types of phagosomes. They were divided, based on their contents, into auto- and heterophagosomes.