Climate change has the potential to influence host-parasite interactions. In this study, we tested how an increase in temperature outside of the common range (12-17. °C) in the Upper Bay of Fundy affected the infection success and impact of a marine parasite (the trematode Gynaecotyla adunca) to its second intermediate host, the intertidal amphipod Corophium volutator. We measured the emergence of G. adunca infectious stages (cercariae) from the first intermediate host, the mud snail Ilyanassa obsoleta, over short (24. h) and long (34. days) time periods, the condition of infected snails, the success of cercariae in penetrating amphipod hosts (infectivity), and the survivorship of infected amphipods. The greatest number of cercariae emerged at 22. °C after 24. h; however, after an initial peak, few cercariae emerged over the longer observation period and there were no consistent temperature effects. Infected snails remained in good condition at the highest temperature (22. °C), as evidenced by their high survivorship and ability to upright themselves. Amphipod host infection (prevalence and intensity) was not affected by temperature. The highest temperature negatively affected amphipod survival, but this did not differ between infected and uninfected hosts. We suggest that increased temperature by itself appears not to result in greater amphipod susceptibility to infection by trematodes or reduced host condition/survival if it is within a naturally-experienced range. While our study indicates no clear and consistent effects of a moderate temperature increase alone on the infection success and impacts of G. adunca in the Upper Bay of Fundy, further studies employing a greater range of temperature extremes and additional abiotic and biotic factors will be needed in order to better understand how climate change may impact the keystone amphipods in nature.

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Keywords Amphipod, Climate, Marine, Parasite, Temperature, Trematode
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Journal Journal of Experimental Marine Biology and Ecology
Shim, K.C. (Kum C.), Koprivnikar, J. (Janet), & Forbes, M. (2013). Variable effects of increased temperature on a trematode parasite and its intertidal hosts. Journal of Experimental Marine Biology and Ecology, 439, 61–68. doi:10.1016/j.jembe.2012.10.016