Scanning electron microscopy of integumental surface of schistosoma mansoni.

The integumental surface of adult S. mansoni was studied by scanning electron microscopy at 50 to 10,000 magnifications. Many spines of variable size cover the inner surface of the oral sucker of the male and extend to the pharyngeal opening. Fewer and smaller globular spines cover the inner surface of the ventral sucker. Bosses of variable size with variable numbers (50 to 250) of spines occur on the greater part of the body surface but not in the gynecophoral canal. The posterior end of the male is devoid of bosses, but spines are freely distributed over the surface. The dorsal body surface is also characterized by papillalike integumental elevations of irregular size, shape, and distribution. These may be associated with clumps of small spines, and in some instances possess a cavity or crater. Larger spines protrude from some of the cavities. The female is free of bosses, but there is a heavy covering of anteriorly directed spines on the posterior part of the body. The structure of the integument of the schistosomes, particularly Schistosoma mansoni, has been investigated employing ultrathin sections suitable for examination in transmission electron microscopy (TEM) (Senft et al., 1961; Morris and Threadgold, 1968; Silk et al., 1969; Smith et al., 1969). These studies have indicated that the integument is a syncytium made up of a surface layer recognized as a cytoplasmic sheath or matrix, connected by cellular extensions to cell bodies (nuclei) buried in the parenchyma. Additionally, there are ultrastructural objects including mitochondria, cuticular channels, vesicles, and discoid granules. Golgi bodies, endoplasmic reticulum, and ribosomes are absent. Contrasted with the abundance of information dealing with subsurface integument, there is a paucity of observations, at comparable magnifications, made on the surface of the schistosome. This is understandable since there was no readily available means of examining the ultrastructure of surfaces other than by utilizing the incalculably small amount of information which could be derived Received for publication 23 March 1972. *Investigation supported by the United StatesJapan Cooperative Medical Science Program administered by the NIAID, NIH, Department of Health, Education, and Welfare, under Grant No. 5 R 22 AI-08207. t Department of Pathology and Laboratories, Nassau County Medical Center, East Meadow, New York 11554. t Division of Microbiology and Infectious Diseases, Southwest Foundation for Research and Education, San Antonio, Texas 78228. from nonsequential ultrathin TEM sections which pass through the surface. The roughness of the surface of the male S. mansoni and, conversely, the smoothness of the female first was recognized employing light microscopy. By this means it was possible to identify many elevated areas which were designated as tubercles covered with hairs. With the development of TEM came a change in nomenclature, i.e., the tubercles became bosses and the hairs became spines. Additionally, TEM occasionally revealed sections through such surface structures as openings of canaliculi and pores of various types. The present report is concerned with the surface microtopography of the adult S. mansoni as visualized with the scanning electron microcope (SEM). The SEM, with its great depth of field, i.e., at least 200 times that of a light microscope, and its resolution of 200 A or better, provides a means for determining the fine topography of body surfaces. Furthermore, an opportunity is afforded to correlate external features with those internal structures revealed by TEM. Other studies dealing with the ultrastructure of the schistosome surface are in progress and involve the use of specimens of known ages from 1 day to 27 weeks, i.e., from the schistosomule to the mature adults. By this means the maturation of surface structures may be correlated with time. To date, the SEM has been used by Hockley (1968), Johnson and Moriearty (1969), and Robson and Erasmus (1970) to study the surface features of the cercariae of S. mansoni, and by