Diet assimilation trends and host-parasite relationships in two species of sunfish (Lepomis) revealed by stable isotope analyses of multiple tissues.

White grub flukes, Posthodiplostomum minimum centrarchi (Trematoda), and hookworms Pomphorhynchus bulbocolli (Acanthocephala) are common internal parasites for many North American freshwater fishes. P. minimum are found as cysts in internal organ tissues, while P. bulbocolli are found as sexually mature adults in gastrointestinal (GI) tracts. Stable isotopes of carbon and nitrogen (δ13 C and δ15 N) are commonly used to infer food web relationships in freshwater lakes. To see if δ13 C and δ15 N could be used to analyze parasite-host relationships, we analyzed the stable isotopes of the two species of parasites and various tissue types of their fish hosts (bluegill and pumpkinseed sunfish) from different host tissues. The samples δ13 C and δ15 N demonstrated that P. minimum and P. bulbocolli fed on the fish hosts livers and intestines, respectively. It is also corroborated by correlations in C/N ratios of those fish parasites and their fish host tissues. This study highlights the importance of identifying the specific host tissues parasites feed on in stable isotope analysis.