Detection of arsenic, mercury, cadmium and lead compounds in Calliphora vicina (Diptera: Calliphoridae) larvae and their potential impact on larval development

Heavy metal exposure represents a substantial health risk to humans and other animals, in some cases leading to death. However, detecting these metals in decaying corpses can pose a considerable challenge. In such situations, the eventual presence of necrophagous insects feeding on the remains may serve as a valuable tool for detecting and measuring these toxic substances. Nonetheless, heavy metals might affect insect development and survival rates. This study explored the effects of increasing concentrations of arsenic, mercury, cadmium and lead compounds on the survival and development rate of Calliphora vicina (Robineau Desvoidy, 1830) (Diptera: Calliphoridae) larvae. Additionally, the research investigated the possibility of tracing these metals in the developed larvae and whether bioaccumulation occurred. The larvae were reared in a dog food matrix infused with varying concentrations of these heavy metal compounds, ranging from 0.0 (control) to 60 mg/kg. The results showed that all tested metals increased mortality rates in a non-linear dose-dependent manner. Higher concentrations of each metal limited larval growth, as evidenced by lower length and weight than the control group. This growth inhibition could lead to inaccurate post-mortem estimations based on entomological evidence collected in heavily contaminated substrates. All metals were successfully detected in the larvae; however, bioaccumulation was only confirmed for cadmium at low concentrations. Therefore, C. vicina larvae can serve as a valuable toxicological indicator for these elements, especially when larvae are found in the corpses of individuals chronically exposed to the assessed heavy metals.