Chemical attraction in the absence of worm-mediated tactile behavior in Trichinella spiralis.

In vitro chemical attraction of Trichinella spiralis was studied using as migrators individual male or female worms. Both male and female worms exhibited a dose-dependent behavior at target doses of 20 to 80 worms, no significant differences in response at doses of 80 to 200 worms, and an inhibition of movement at doses of 200 to 400 worms. Single males were attracted less to a mixture of males and females as the source of pheromone than single males to a female source. Single females did not move significantly towards a mixture of males and females. Adult males and fourth-state, juvenile males were significantly attracted to fourth-stage females as the pheromone source. Fourth-stage males attracted adult females but not forth-stage juvenile females. Adult males and females and third-stage, juvenile males and females were not significantly attracted to a pheromone source from third-stage juvenile males and females. We postulate that the onset of pheromone production in T spiralis is during the fourth developmental stage.