Comparison of the surface morphology of adult Schistosoma japonicum (Chinese, Philippine and Indonesian strains) by scanning electron microscopy

Abstract

Comparison of the surface morphology of adult Schistosoma japonicum (Chinese, Philippine and Indonesian strains) by scanning electron microscopy. International Journal for Parasitology 16: 205–216. When viewed by scanning electron microscopy, the surfaces of Chinese, Philippine and Indonesian strains of S. japonicum are highly spongy and consist of ridges and papillae. Among males there are differences in the number and distribution of papillae and the pattern of ridges. Three kinds of papillae were observed: (1) the large fungiform papillae (3–4 μm in diameter, most without cilia) are more numerous in Philippine and Indonesian strains; they concentrate on the lateral aspect of the anterior and middle parts close to the edges of the gynecophoral canal, and on the latero-dorsal aspect of the posterior part and the tail; (2) in all strains, small ciliated hemispherical papillae (1.5–2 μm in diameter) are numerous, especially in and around the suckers, the gynecophoral canal, and on the tail, elsewhere they are evenly distributed; (3) the cratered papillae (3–4 μm in diameter, about half bearing cilia) are most numerous in the Indonesian strain but are very few in the Chinese strain; they concentrate on the lateral aspect of the middle part and on the edges of the gynecophoral canal. Ridges (about 0.2–0.6 μm in width) are long, thin, wavy and least branching in the Chinese strain. They are thicker and more branching in the Philippine and Indonesian strains. Furthermore, in the latter two there are leaf-like projections and microvilli on the posterior half of the body surface; these cover a greater area of tegument in the Indonesian strain. Spines are present only on the tail end; they are large and more numerous in the Philippine and Indonesian strains. In contrast to males, the surfaces of females are relatively similar. There are spines on all areas except the most anterior end where a large number of long cilia are present. Fungiform papillae are more numerous on females of the Philippine and Indonesian strains, and they concentrate on the latero-dorsal aspects of the middle and posterior parts and around the excretory pore. Ridges in all females are not so well developed and are present only in the middle part of the body.