Combined effects of copper and cadmium exposure on ovarian function and structure in Nile Tilapia (Oreochromis niloticus)

With the rapid development of industrialization and urbanization, the issue of copper (Cu) and cadmium (Cd) pollution in aquatic ecosystems has become increasingly severe, posing threats to the ovarian tissue and reproductive capacity of aquatic organisms. However, the combined effects of Cu and Cd on the ovarian development of fish and other aquatic species remain unclear. In this study, female Nile tilapia (Oreochromis niloticus) were individually or co-exposed to Cu and/or Cd in water. Ovarian and serum samples were collected at 15, 30, 60, 90, and 120 days, and the bioaccumulation, ovarian development, and hormone secretion were analyzed. Results showed that both single and combined exposure significantly reduced the gonadosomatic index and serum hormone levels, upregulated estrogen receptor (er) and progesterone receptor (pr) gene transcription levels, and markedly affected ovarian metabolite levels. Combined exposure led to more adverse effects than single exposure. The data demonstrate that the Cu and Cd exposure can impair ovarian function and structure, with more pronounced adverse effects under Cu and Cd co-exposure. The Cu and Cd affect the metabolic pathways of nucleotides and amino acids, leading to ovarian damage. This study highlights the importance of considering combined toxicant exposure in aquatic toxicology research and provides insights into the potential mechanisms underlying heavy metal-induced reproductive toxicity in fish.