Normal development of Schistosomatium douthitti in the snail Lymnaea catascopium.

Schistosomatium douthitti miracidia are ingested by Lymnaea catascopium snails and penetrate the host's esophageal wall. Mother sporocysts develop adjacent to the esophagus and salivary glands. The increase greatly in size, become irregular in shape, and contain daughter sporocysts by 8 days. Development of daughter sporocysts is synchronous; most are released from mother sporocysts 16--20 days postexposure. Mother sporocysts then collapse, but may persist for the life of the infected snail. Some daughter sporocysts travel to the digestive gland via the arterial system; others traverse the connective tissue separating cephalopedal and visceral sinuses to reach the digestive gland. Cercarial embryo production begins while daughter sporocysts are still within mother sporocysts, and may continue for over 400 days. Once released from daughter sporocysts, cercariae move from the visceral sinus to the visceral vein and are carried into the mantle where they rupture the ventral mantle epithelium and escape from the molluscan host.