Low levels of inorganic copper impair reproduction parameters in Oreochromis niloticus after chronic exposure

Abstract

Copper (Cu) is an essential metal utilized in aquaculture activities for both nutritional and disease control. Conversely, this metal can present a risk of exposure to biota depending on the used concentration, but data are still scarce and studies to establish the real risk of copper exposure to fish even in aquaculture activities are welcome. To evaluate a set of environmentally realistic doses of inorganic copper and so the potential risk of exposure to reproduction, Oreochromis niloticus were orally exposed to 0.1, 1.0 or 10.0 mg Cu.kg−1 body weight for 60 days (one dose each 10 days). Parameters regarding sperm quality, including viability, membrane integrity, mitochondrial functionality, apoptosis, lipid peroxidation, protein carbonylation, DNA integrity and motility were considered as signs of reproductive impairment. Additionally, as copper is also described as a pro-oxidant metal, we investigated the oxidative balance in liver (Non-protein reduced thiols concentrations-GSH, superoxide dismutase activity-SOD, lipid peroxidation-LPO, protein carbonylation-PCO and glutathione S-transferase-GST activity). Fishes exposed to copper showed poor sperm quality due to the observed reduced motility and motility period. Induced mitochondrial dysfunction, lipid peroxidation and apoptosis in germ cells, as well as DNA fragmentation confirms the high impairment of Cu to reproduction of O. niloticus exposed to copper in realistic doses. Exposure to the highest dose used in this experiment led to oxidative imbalance in liver, corroborating the deleterious effects of this metal to biological systems. These findings strongly suggest that even under very low Cu doses, or realistic doses as utilized in aquaculture activities, the metal may negatively affect O. niloticus reproduction, probably decreasing the success of aquaculture activities.