Intra-Body Variations of Stable Isotope Ratios (δ13C, δ15N) and Influence of Storage Methods in Aquatic and Post-Aquatic Stages of the Common Toad, Bufo bufo

Isotopic signatures of carbon and nitrogen are widely used for analysis of the structure of food webs in aquatic ecosystems. The study of animals raises a number of methodological questions, including choice of representative tissues and organs for sampling as well as storage of the studied organisms. Furthermore, the impacts of preservation methods can be tissue-specific, age-specific, and even taxon-specific; thus, studies of these impacts on particular taxa are necessary. We focused on the C and N isotope composition of the common toad (Bufo bufo), one of the most widespread European anuran amphibians. We hypothesized that its different tissues and organs may vary in isotopic composition, and ethanol and freezing may have different effects on isotopic values. Our results showed that both tissue and storage method factors significantly affected the delta C-13 values of tadpoles and postmetamorphic juveniles, whereas only the tissue factor had a significant effect on the delta N-15 values. The two stages, tadpoles and postmetamorphs, should be analyzed separately despite the brief postmetamorphic period of the juveniles. The skin, legs, muscles, and tail in tadpoles and legs, muscles and heart in juveniles can be used for delta C-13 and delta N-15 analysis regardless of the method of storage. The results will serve for the optimization of future study designs in isotopic ecology.

Automated summary

Isotopic signatures of carbon and nitrogen are widely used for analyzing food web structures in aquatic ecosystems. The study highlights the importance of considering the effects of different tissues, storage methods, and preservation on isotopic values in animals. Different tissues of tadpoles and postmetamorphic juveniles may vary in isotopic composition.