Cell atlases of schistosome human infective stages reveal larval tissue fates and innovations

Schistosomes infect over 250 million people, yet the cellular basis of their human-infective cercaria larva, that drives transmission and infection, remains poorly understood. We present single-cell atlases of Schistosoma mansoni cercariae, widely regarded as transcriptionally quiescent, and schistosomula, the first intra-mammalian stage. Twenty-two cercarial cell types either persist into schistosomula or are lost. The tail harbours several cercaria-specific innovations, including a novel tegument. Gene-age analysis supports the cercaria as the most recent addition to the life cycle and tail cells as younger than body cells. Persisting cell types undergo clear transcriptional transitions which give new insights into the dynamics of cercarial transformation into schistosomula. These findings link the recent origin of cercarial cell types to the evolution of active dispersal and transmission in digenean parasites.