Influence of lipid extraction in the muscle tissue of the blue crab Callinectes sapidus Rathbun, 1896 (Decapoda: Brachyura: Portunidae) in the determination of δ13C and δ15N

Stable isotope analysis of delta C-13 and delta N-15 has been used in the description of the trophic ecology in marine organisms. This approach has been applied to various taxa including crustaceans. Pre-treatment of samples before isotope quantification is suggested for tissues with high lipid content, because lipids can affect the isotope concentrations. We focused on the isotope analysis of tissues of the blue crab (Callinectes sapidus) because it is a significant prey item for intermediate and top predators. We aimed to assess the isotope values produced by two lipid extraction methods and compare these results with values of samples which were not lipid-extracted. Results evidenced a negative relationship between Delta delta C-13 and the C:N ratios, the C:N ratios explaining 98% of the variation in the Delta delta C-13. Regarding the SEAc results, the delta C-13 values showed more negative values after the lipid extraction Bligh and Dryer method, which indicates that this method is accurate for pre-treatment of samples before isotope quantification. These results highlighted the importance of lipid extraction before quantifying isotopes and enforces the need of pre-treatment of samples.