[Host-parasite relations of the trematode Microphallus papillorobustus (Rankin 1940). III Factors involved in the behavioral changes of the Gammarus, intermediate hosts and predator tests].

The responses of infected and uninfected Gammarus to certain stimuli are experimentally studied. Under the influence of the cerebral metacercaria of Microphallus papillorobustus , the light preferendum of the Gammarids is shifted towards an area of higher illumination, the phototactism becomes strongly positive, the geotactism is reversed from positive to negative, the responses to mechanical disturbances are altered. Predator tests show that infected Gammarids are more vulnerable than uninfected ones to predation by one of the definitive host of the Trematode, Larus cachinnans . Thus the transmission is favoured.