Toxicological effects of 2,6-dimethylphenol on Galleria mellonella : insights into immunotoxicity and cuticular barrier disruption

Environmental exposure to industrial phenolic compounds poses growing concerns for insect biodiversity and ecosystem health. This study investigates the toxicological and physiological effects of 2,6-dimethylphenol (2,6-DMP), a widely used phenolic pollutant, in Galleria mellonella (the greater wax moth), a species of ecological importance and a major pest associated with honeybee colonies. Topical application of 2,6-DMP resulted in significant larval mortality (median lethal dose = 3.77 µg/mg body wt), while adults displayed reduced sensitivity, suggesting stage-dependent toxicodynamics. In vivo assays revealed immunotoxic effects, including hemocyte deformation, decreased viability, and marked depletion of cuticular free fatty acids critical for maintaining the insect's barrier function. Supporting in vitro experiments confirmed dose-dependent cytotoxicity in insect hemocytes and Sf9 cell lines, likely due to membrane disruption. Given the ecological association of G. mellonella with honeybee colonies, our results provide context for evaluating potential risks of phenolic contaminants within agricultural systems. Moreover, phenolic compounds such as 2,6-DMP are known to affect aquatic invertebrates, and the mechanisms identified here may contribute to understanding their broader ecological impact.