Determination of toxic elements in the life cycle stages of necrophagous flies at a landfill in Mae Pa Sub-District, Tak Province, Thailand

Abstract

This study examined the diversity and accumulation of potentially toxic elements (PTEs) in necrophagous flies associated with a landfill in Mae Pa Sub-district, Tak Province, Thailand. A total of 1,470 specimens representing nine species from six genera were collected, with Calliphoridae (49.52%) and Muscidae (43.89%) as the dominant families. The assemblage was mainly composed of Chrysomya megacephala (83.95% of blow flies) and Musca domestica (90.40% of muscid flies). The population showed a female-biased sex ratio, with females comprising 62.24% of specimens (female:male = 1.65:1), reflecting sex-specific feeding and reproductive behaviors. Morphological analysis showed that eggs represented the shortest developmental stage, whereas larvae were the longest (11.4–18.4 mm), with P. dux generally larger than C. megacephala. X-ray fluorescence analysis revealed potassium (0.04–48.0%), calcium (14.2–41.4%), and magnesium (7.1–28.7%) as the predominant elements in surface whole-body elemental mapping across all life stages, reflecting essential macronutrients associated with dietary composition and nutrient assimilation. Furthermore, targeted PTE accumulation, determined by ICP-MS, varied among species, sex, and developmental stage. Adult female C. megacephala accumulated significantly higher levels of cadmium, copper, and iron (p < 0.05) than other adults, likely reflecting greater dietary exposure due to intensified foraging behavior and increased micronutrient requirements for ovarian maturation and oogenesis. Overall, necrophagous flies effectively integrate environmental metal contamination across life stages, supporting their use as bioindicators for environmental monitoring.