Observation of developing cercaria of Schistosoma japonicum on ultrastructural level and remarks at its morphology of mature stage

To study the developing cercaria of Schistosoma Japonicum (S. japonicum) on ultrastructural level by transmission electron microscope (TEM) for analyzing the morphological dynamic changes of the tegument, glands and musculature. Artificial infected Oncomelania hupensis were dissected under dissecting microscope and the daughter sporocysts picked up for studying the germinal cells stage (S1). The other embryonic cercaria were selected according to the modified parameter of Chen and Bier (1972). The specimens were prepared by conventional procedure of the laboratory of TEM and were observed by Hitachi H600. Beside the germinal cell stage (S1), this is the first chronological study on the morphological development of S. japonicum cercaria from S2-S5 concerning the tegument and its elements (glycocalyx, sensory papilla, basal lamina and spine), head and acetabular gland and musculature of the body and tail. This article discusses the ultrastructural morphological differences from prior authors and emphasizes on the postacetalar gland and the pattern of tail musculature of the matured stage cercaria. According to the cell division and differentiation, the process of development may be divided into 5 stages: S1, the single germinal cell stage; S2, the germinal ball stages: major multiplication and minor differentiation; S3, tail budding embryonic stage, both active in multiplying and differentiating; S4, the pre-matured stage, major differentiation and minor multiplication; and S5, the fully matured stage (completing the differentiation).