[M-IS09] Biogeochemistry

[MIS09-P04] Specific stable isotope ratios of freshwater fish parasites using amino acid stable isotope ratio analysis

*Kei Kinoshita¹, Naoto Ishikawa², Keisuke Kaba¹ (1.Department of biology, Graduate School of Science, Kyoto University, 2.Japan agency for marine-earth science and technology)

Keywords:stable isotope, parasite, ecology

Parasites are widely distributed in diverse environments, both terrestrial and aquatic, and it is estimated that more than half of all organisms are parasites. Parasites in freshwater ecosystems utilize multiple host organisms in their life cycles and use predator-prey relationships among hosts to move to hosts with higher trophic levels, so the trophic level of parasitoids is thought to change at each developmental stage.
Carbon and nitrogen stable isotope ratio analysis has been used to estimate the trophic level of organisms. On the other hand, studies of freshwater fish parasitoids have reported significant variation in the degree of enrichment among parasite species. This result may be due to the fact that the exact food utilization of parasitoid species has not been clarified.
Therefore, in this study, we attempted to evaluate the trophic level of parasitoid species of Opsariichthys uncirostris family Carabidae of Lake Biwa using amino acid nitrogen stable isotope ratio analysis, which can also evaluate the food use of parasitoid species.
Among the parasitoid species examined, hookworms, which have lower nitrogen stable isotope ratios than their food-using hosts, showed lower trophic levels than their food-using hosts in trophic level estimation using glutamate and phenylalanine. This is similar to the specific results obtained by carbon and nitrogen stable isotope ratio analysis, which will be discussed.