Development of Sarcocystis falcatula in cell cultures demonstrates that itis different from Sarcocystis neurona

The development of Sarcocystis falcatula merozoites in bovine turbinate (BT ) cell cultures is described and compared with development of Sarcocystis n eurona merozoites. Merozoites of S. falcatula entered BT cell cultures and increased in size until 3 days post-inoculation when the nucleus of some me rozoites developed lobes. Developing schizonts present at 4 days contained a lobed nucleus or appeared multinucleate. A single mature schizont was obs erved 4 days p.i. Schizonts were numerous 5 and 6 days p.i. Merozoites were produced from blastophores on the schizont. S. neurona merozoites develope d to mature schizonts by 3 days p.i. in BT cells and a residual body was of ten present. Transmission electron microscopy revealed that S. falcatula me rozoites possessed more micronemes than did S. neurona merozoites. Our stud y demonstrates that S. falcatula and S. neurona are not the same parasite.