Effect of parasite on predation and salinity tolerance during invasion

Gammarids as intermediate hosts of the , Polymorphus minutus, are known to be subject to alterations of behavior, which fosters the transition of the parasite to birds as final hosts. In order to assess the effect of parasites on predation ,which could ultimately affect the invasion success of gammarids, we first investigated the avoidance behavior of parasitized native and invasive gammarids based on cues emitted by three-spined sticklebacks, Gasterosteus aculeatus, as non-host predator. We hypothesized higher avoidance of non-host predator in parasitized native and invasive gammarids because of manipulation by the parasite. Second, we tested the hypothesis that native and invasive gammarids species respond differently when they have not been parasitized. Test animals were gammarids of the Paderborn plateau (Westphalia, Germany), namely the sympatric species Gammarus pulex and G. fossarum, native of this region, and Echinogammarus berilloni, representing the invader. Laboratory experiments with Y shaped maze were conducted in a climate chamber. parasitized native and invasive gammarids, and unparasitized native gammarids do not avoid the non-host predator, the three-spined stickleback, than unparasitized invasive E. berilloni. In another experiment, We predicted that there is high salinity tolerance in non parasitized invasive species and also this parasite increases salinity tolerance of all there intermediate hosts. Comparing natives vs. invasive specimen in Kaplan-Meier survival analysis test, we obtained the following results: Both non parasitized and parasitized E. berilloni showed significantly higher salinity tolerance compared to both non parasitized and parasitized natives. Our results contribute tothe understanding the role of increased environmental tolerance to invasion success.

Keywords:

Invasion , Stalinity tolerance , Paderborn plateau , gammarids