FLIM as an identification tool for stress responses in mussel Mytilus galloprovincialis under cadmium exposure

Abstract

With the rapid development of modern industry, heavy metal pollution is becoming one of the most severe marine environmental problems among the world. Mussels are considered as suitable models to monitor heavy metal pollutions. The hematoxylin and eosin (H&E) sections of mussels could be observed with fluorescence lifetime imaging microscopy (FLIM) method, generating quantitative data of images for improved analysis with higher accuracy. In this study, we used FLIM method to investigate the fluorescence lifetime of digestive glands of adult mussels Mytilus galloprovincialis treated with two environmentally relevant concentrations (5 μg/L and 50 μg/L) of cadmium (Cd) for 14 days. After exposure, the H&E stained sections of the digestive glands were observed with FLIM system. The images were analyzed with SPCImage software, providing both the structural images with fluorescence intensity information and the pseudo-color images with fluorescence lifetime information. The fluorescence lifetime values were presented as total τ, which could be divided into τ1 (the shorter part) and τ2 (the longer part), respectively. Results showed that the τ2 values in 50 μg/L Cd treatments were significantly lower than those of the control group, suggesting that the high concentration of Cd treatment has a high impact on the digestive glands of M. galloprovincialis. The significance of the fluorescence lifetime data of mussel digestive glands induced by Cd at a high concentration has proved the sensitivity of FLIM method to distinguish the polluted mussels from the healthy individuals. In conclusion, FLIM has high potential in further applications of marine environment pollution monitoring.