Trematode parasites of mollusc hosts from marginal seas and their sensitivity to warming

Parasites, like the diverse Digenean trematodes, are crucial to ecosystems, influencing everything from ecological speciation to food webs and host behavior. However, knowledge deficits persist regarding their biodiversity, life cycles, and geographical distribution, which complicates our broader understanding of ecosystems and response to the crisis in biodiversity. Some parasites risk extinction before they are discovered, especially in rapidly warming Marginal Seas such as the Persian Gulf and Baltic Sea, as a result of the ongoing global warming accelerated by human activity. Therefore, it is imperative to investigate the effects of warming on host-parasite systems in these regions and to comprehend the thermal performance of parasites. This is especially true as basic information such as parasite biodiversity is still missing in some regions, while the impact of environmental change on parasite performance remains largely unknown even in well-studied areas.

Within four chapters, this thesis aimed to explore the yet unknown trematode biodiversity in the Persian and Oman Gulfs via molecular identification of trematodes infecting the most abundant mud snail Pirenella cingulata. Next, we investigate the thermal sensitivity of two prevalent trematodes (Acanthotrema tridactyla and Cyathocotylidae gen. sp) infecting P. cingulata. Lastly, this thesis investigates the combined effect of warming and parasitism on mussel performance using Renicola roscovita infecting Mytilus edulis as the host-parasite system in the Baltic Sea.