Developmental Studies on the Digestive Tract of Schistosomules (Schistosoma mansoni) Grown in vitro. I. Ultrastructure

Abstract

Schistosomules of S. mansoni were recovered and incubated in culture medium following penetration of excised mouse skin. The development of the digestive tract was studied at the ultrastructural level for the first 15 days in vitro. The effect of red blood cells on this development was monitored. Some of the schistosomules were offered red blood cells on days 0-4, but the first indications of feeding were not demonstrable until day 6 post-penetration. At that time dense deposits of pigment were observed in the lumen of the ceca. The esophageal gland cells synthesized crystalline granules at day 4 post-penetration. These were observed in the cells and in the lining of the posterior region of the esophagus. The number remained relatively small unless red blood cells were ingested by the schistosomules, at which time the number of granules increased significantly. Since the cytoarchitecture of the cells manifests the requisites for synthetic activities (e.g., rough endoplasmic reticulum, Golgi complexes) prior to addition of red blood cells, the ingestion of red blood cells probably stimulates an increase in synthesis of the granules. The ultrastructure of the developing ceca was similar to comparable regions in the adult. Ingestion of red blood cells stimulated formation of new surface amplifications and a general increase in size.