SUMMARY: Researchers discovered that a new molecule produced by the rotifer, Rotaria rotatoria, paralyzes cercariae. Cercariae are the free-living/infectious stage of the flatworm Schistosoma, the cause of schistosomiasis. R. rotatoria live on the shell of freshwater snails and secrete a compound scientists have named Schistosome Paralysis Factor or SPF, into the water. It causes cercariae to stop swimming and sink to the bottom and it also prevents cercariae from infecting mammals. SPF is dose dependent, which means the higher the dose, the faster and longer the cercariae stay paralyzed. Researchers have also found that Streptomyces (a type of bacteria) produce similar compounds, but these bacterial products don’t worked as well as SPF (only one was effective at paralyzing cercariae). No one knows why these rotifers produce this compound.
LESSON COMMENTS: This article can be used in many ways. For elementary kids, teachers can use this to address clean water issues around the world. For middle school students, this article can be used when the class is learning about ecosystem relationships. This is a great example of amensalism. High school environmental science classes can delve deeper into this relationship and teachers can encourage students to find other articles that look at similar relationships. Finally, chemistry or biology teachers can use this article to talk about the molecular structure of SPF and the other two compounds produced by the Streptomyces. The second to last subsection in results and discussion talks about differences in structure between all three compounds. One of the bacterial compounds isn’t a paralytic at all and the structure suggests that this is due to an extra methyl group.
Gao, J., Yang, N., Lewis, F. A., Yau, P., Collins, J. J., 3rd, Sweedler, J. V., & Newmark, P. A. (2019). A rotifer-derived paralytic compound prevents transmission of schistosomiasis to a mammalian host. PLoS biology, 17(10), e3000485. doi:10.1371/journal.pbio.3000485