Elevated copper exposure alter growth, amino acid profile and metal bioaccumulation in black soldier fly (Hermetia illucens).

Copper is an essential microelement for energy metabolism and serves as an enzyme cofactor; however, high concentrations cause toxicity and lead to contamination in black soldier fly larvae (BSFL; Hermetia illucens; Diptera: Stratiomyidae) production for feed and food. This study assessed the effects of high-dose Cu exposure on the growth, substrate conversion, mortality rate, Cu bioaccumulation, and nutritional quality of BSFL. Six-day-old larvae were reared for 10 d on substrates supplemented with copper(II) sulfate pentahydrate (CuSO4·5H2O) at six concentrations: T0 = 0.01; T1 = 436; T2 = 868; T3 = 1312; T4 = 1744; and T5 = 2182 mg kg-1 dry matter (DM). The results indicated a clear dose-dependent response, where increasing Cu exposure progressively reduced the final body weight and weight gain (p < 0.010). A relative tolerance was observed at the medium dose (436 mg kg-1 DM, where performance did not differ significantly from that of the control. In contrast, high-dose exposure (≥868 mg kg-1 DM) caused a marked decline in growth performance, with the most severe effect observed at 2182 mg kg-1 DM (T5). A dose of 436 mg kg-1 DM represents the peak of bioaccumulation but decreases at higher doses. This pattern indicates a physiological mechanism of saturation or enhanced excretion. The Cu content in BSFL biomass reached a maximum of 26.3 mg kg-1 DM and remains within the safe feed limits established by the European Food Safety Authority (15-170 mg kg-1 DM). The level of essential amino acids (arginine, histidine, and phenylalanine) decreased significantly under Cu treatment ≥436 mg kg-1, as confirmed by multivariate analysis (p < 0.050, KMO = 0.636). In conclusion, Cu exposure reduces BSFL production by altering physiology and nutritional quality, with 868 mg kg-1 serving as the critical threshold for growth and amino acid composition.