Diet-switch experiments in two parasite-host systems have been performed, taking samples for stable isotope analyses (both bulk stable isotope analyses and compound-specific stable isotopes of amino acids) from both the host and the parasite. Isotopic differences between parasites and their hosts (i.e. trophic discrimination factors) as well as between infected and uninfected hosts have been calculated, two datasets have been produced and are now statistically being analyzed and prepared for publication. These datasets have been complemented by including field-based samples, which will help to understand naturally occurring stable isotope signals in parasite-host systems. Preliminary results suggest that the changes over time in 13C and 15N happen at different rates in infected and uninfected snails, i.e. the turnover time is different, especially in the digestive gland versus the muscle. This is likely caused by the presence of parasites, showing different stable isotope values in infected individuals, which could lead to potential errors in estimation of trophic niches and positions in food webs.
We also have developed a conceptual model to advance our understanding of trophic parasitic relationships, describing how changes in resource intake or internal resource use of hosts caused by parasites can lead to differences of trophic and isotopic niches of infected versus uninfected individuals and ultimately alter resource flows through food webs. This resulted in a publication in a leading parasitology journal (Trends in Parasitology, 39:749–759. 10.1016/j.pt.2023.06.003).
Furthermore, preliminary analyses have been presented at five conferences or scientific seminars, two other manuscripts are being prepared to present the obtained results, in addition to other manuscripts published during the project. The results have been also disseminated in several outreach activities, press releases and an interview.
