Autofluorescence and Fourier transform infrared analyses trace dietary fluorophores and reveal plastic contamination in the gut of mosquito larvae

Understanding the nutritional physiology of mosquito larvae is crucial for optimizing mass-rearing practices and improving control strategies. Here we combined complementary optical and spectroscopic techniques, including fluorescence microscopy, confocal spectral imaging and Attenuated Total Reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy, to trace food ingestion in Aedes albopictus larvae. Differences in autofluorescence (AF) signal intensity and spatial distribution were observed in the gut of larvae reared in polystyrene (PS) or glass (GL) containers, suggesting that AF may serve as a relative proxy for evaluating ingestion efficiency. Chlorophyll-derived AF was detected outside the gut within the larval body, indicating systemic distribution of food-derived fluorophores. Spectral analysis of rearing water before and after larval development revealed changes in flavin-associated fluorescence profiles, consistent with flavin metabolism. Moreover, ATR-FTIR spectroscopy of larval gut samples revealed differences in chemical functional groups between larvae reared in PS or GL containers, suggesting ingestion of PS-derived material released from rearing containers. Despite the spectroscopic differences observed between rearing conditions, no clear effects were detected on standard mosquito life-history traits. Taken together, these findings highlight the potential of fluorescence- and ATR-FTIR-based techniques as sensitive tools to explore mosquito larval biology and nutrition. These approaches can reveal subtle yet biologically relevant effects of the rearing environment, a key factor in vector control programmes.