Cadmium Exposure as a Potential Threat to the Ecological Services of the Giant Water Bug Belostoma anurum

Freshwater ecosystems are often exposed to anthropogenic contaminants that can unbalance the aquatic fauna equilibrium and disrupt key ecological services naturally provided by aquatic organisms. Freshwater environments face increasing contamination by heavy metals such as cadmium (Cd). Here, we evaluated the toxicity of cadmium to Belostoma anurum, a giant water bug capable of preying upon larvae of Aedes aegypti mosquitoes. We first compared the sensitivity of predator and prey to cadmium using concentration-response assays. Then, we investigated whether sublethal exposure to cadmium would affect redox biology biomarkers, survival, and the ability of B. anurum to prey upon A. aegypti larvae under different prey densities. Cadmium was 33.6 times more toxic to B. anurum nymphs (LC50 = 1.6 μg/mL) than to A. aegypti larvae (LC50 = 54.1 μg/mL). Additionally, continuous exposure of B. anurum nymphs to a low cadmium concentration (LC10 = 0.19 μg/mL) resulted in significantly increased malondialdehyde levels and reduced survival abilities compared to unexposed nymphs. However, sublethal exposure did not impair the predatory abilities of B. anurum nymphs across different mosquito larvae densities. Collectively, our findings suggest that cadmium contamination can negatively affect giant water bug populations in freshwater ecosystems, potentially weakening their ecological service as natural biological control agents of mosquito populations.