Schistosoma mansoni: morphologic changes induced by maintenance in vitro.

Adults of Schistosoma mansoni were incubated in several culture media at various time intervals ranging from 2 to 96 hr. The morphologic changes induced by the incubation were documented using both scanning and transmission electron microscopy. These included changes in the tegument, esophageal cells, and cecum. Variability was noted among worms within experimental groups and the surface changes on single worms were frequently observed to have patchy distribution. Based on morphologic changes observed, culture media were ranked as adequate, mediocre, or inadequate. RPMI-1640 + 50% fetal calf serum, Eagle's MEM with Earle's salts (no serum), and McCoy's 5A Medium + serum were judged adequate. Basal Eagle's Medium, Triple Eagle Medium, NCTC-135, and Earle's Balanced Salt Solution (all with or without serum) were judged mediocre. Hanks' Basal Salt Solution (with or without serum) was judged as severely inadequate. All media tested gave better results in the presence of serum. These factors point to the necessity for the use of carefully selected culture media, as well as adequate controls and sampling techniques in the interpretation of in vitro experiments with S. mansoni.