Abstract
Studies were made on the development of Theileria sergenti in the midgut of the nymphal tick vector, Haemaphysalis longicornis. In 10hr post-repletion, merozoites were observed in or outside of erythrocytes infected with T. sergenti in the contents of the midgut of the tick. Within 24hr post-repletion, many merozoites were noticed outside of erythrocytes. They were 1.0-2.5μm in size, and round, and comma-shaped, or spindle-shaped. After that, these merozoites were transformed into ring-forms which were comparatively large ring 1-2μm in diameter. Within 48-72hr post-repletion, ring-formed protozoa developed into eosinophilic macrogametes 3-4μm in diameter and spindle-shaped protozoa which were considered as microgametes 5μm in length. Within 3-5 days post-repletion, round or elliptic zygotes were observed in the gut. They were 4-5μm in diameter. About 6 days after repletion, zygotes began to decrease gradually in number and disappered finally from the gut. Then round protozoa (4-5μm in diameter) appeared again in the gut epithelial cells.
