Schistosoma mansoni: Adult worm chemoattraction,with and without barriers

Heterosexual and homosexual chemoattraction studies were done with 8- to 12-week-old Schistosoma mansoni adults in linear chambers containing Earle's saline, in the absence and presence of both perforated and unperforated dialysis sac chimney barriers. In the absence of barriers attraction was seen in all heterosexual and homosexual combinations. After 90 min of observation at 37 C, organisms maintained at 4 or 37 C for at least 1 hr prior to the assay showed heterosexual attraction similar to those used immediately after perfusion. There was significantly more heterosexual attraction between worms from same than different pairs. In the presence of perforated barriers the greatest attraction was heterosexual, with males moving toward females; heterosexual attraction with females moving toward males was approximately equal to homosexual female attraction, and male homosexual attraction was not seen. In the presence of unperforated barriers the greatest attraction of females toward males occurred during the first 0.5 hr; within 3 to 4 hr females were no longer significantly attracted to males. However, after 0.5 hr males were more significantly attracted to females in unperforated than perforated chimneys. These studies demonstrate that adult schistosomes attract each other in vitro, and that there is a chemical basis for this attraction.