Multi-level assessment of chronic toxicity of the insect growth regulator lufenuron in the non-target aquatic organism Daphnia magna

Lufenuron, a benzoylurea insect growth regulator, is widely used against various pest species. Despite its broad application, multi-level studies addressing the chronic and sublethal effects of lufenuron on Daphnia magna remain limited. In this study, we evaluated the physiological, biochemical, and transcriptional responses of D. magna exposed to three lufenuron concentrations (0.01, 0.025, and 0.06 µg/L) over 21 days. The 48-h EC50 was determined as 0.383 µg/L. Chronic exposure was associated with decreased survival, body length, molting frequency, and heart rate. Reproductive performance was also impaired, as shown by a reduced total number of offspring per female and delayed first brood. Biochemical analyses showed increased MDA levels and elevated SOD and CAT activities, along with decreased GST activity. Transcriptional analyses revealed significant induction of Nrf2, upregulation of SOD and CAT, suppression of GST at low concentrations, and significant upregulation of CYP360A8, CYP4, HR96P, and P-gp, while CYP314 expression remained unchanged. In addition, VTG expression increased, whereas CUT and DMRT expression decreased, indicating modulation of genes associated with reproduction and development. These results suggest that chronic lufenuron exposure can adversely affect multiple biological endpoints in D. magna and highlight the importance of considering sublethal effects in ecological risk assessment.