Abstract: Objective To compare the morphological features and the development of Raillietina echinobothrida and R. tetragona from chicken. Methods The parasites were collected from chicken digestive tract, and 3-5 fresh scolex fragments were separated. After being washed, fixed, dried, glided by ion sputter, the specimens were observed and photographed under scanning electron microscope. The cestodes were immersed in tap water for natural stretch and proglottids of different development stages were used for serial paraffin sections by conventional method, stained with HE and mounted in gum. Morphological observation was carried out by optical microscopy. The naturally stretched worms were pressed between two glass, stained, dehydrated, cleared, mounted, and observed under optical microscope. Results The body of the two species consists of scolex, neck and strobilae. Each mature proglottid showed a set of male and female reproductive system and genital openings on one side. Testes located on both sides of the ovary and behind vitellarium. A complete worm of R. echinobothrida was shorter than R. tetragona, with a round scolex and suckers and short neck. The ovary looked like leaf and vitellarium was in kidney-shape. There were many acid particles and calcareous corpuscles in gravid proglottids. Egg capsule showed no clear boundary and contained only one egg. However, the scolex and suckers of R. tetragona were oval in shape, and the neck was long and thin. The ovary was flower-like. Each egg capsule contained 4-12 eggs and many calcareous corpuscles, each of which was surrounded by a membrane. The male reproductive system matures first in both species. As the two reproductive systems matured, the proglottids became gravid after fertilization. The formation of egg capsule in the two species was similar. Conclusion There are no significant morphological and development differences between the two species of Raillietina.

Key words: Chicken, Raillietina, Morphology, Development