Intra-body variation and ontogenetic changes in the isotopic composition (13C/12C and 15N/14N) of beetles (Coleoptera)

Stable isotope analysis, which is widely used for studying trophic relationships of invertebrates, requires a correct estimation of trophic fractionation factors as well as the proper choice of reference tissues. Different organs and body parts of large insects may vary in the isotopic composition of carbon (δ13C) and nitrogen (δ15N), though detailed information is available for a limited set of species only. In the field-collected larvae and adults of Oryctes nasicornis (Scarabaeidae) and Uloma rufa (Tenebrionidae), the range of δ13C and δ15N values for different body parts and organs (muscles, legs, wings, elytra, fat body, gonads, etc.) was 4.8‰ and 2.4‰, respectively. We suggest that the muscle tissue or legs of large insects should be preferably selected for isotope analysis. The isotopic composition of nitrogen in beetles did not depend on the ontogenetic stage and was not affected by metamorphosis. In larvae and adults of Tribolium confusum (Tenebrionidae) reared in the laboratory culture, the trophic fractionation factors of carbon (Δ13C) and nitrogen (Δ15N) were within the expected values (from −1 to 1.5‰ and from 3 to 5‰, respectively), though depended on the diet. Changes in the δ13C values during ontogenesis reflected changes in the lipid content and were strongly correlated with the C/N ratio. © 2015, Pleiades Publishing, Inc.