Nippostrongylus brasiliensis: factors influencing movement of males toward a female pheromone

Single, responding males of Nippostrongylus brasiliensis exhibited a dose-dependent movement toward a pheromone source that was derived from incubation or homogenization of female helminths in Tyrode's solution. Increases in female homogenate beyond an optimum concentration resulted in reduced male movement toward the pheromone source. Crowding of male N. brasiliensis prior to their exposure to female pheromone gradients diminished the males' response. However, crowding of females had no effect on response to the pheromone. The locomotory responses of males exposed to various mixed male and female pheromone sources reaffirmed earlier suggestions of a pheromone feedback system in which males influence the pheromone released from females.