Fate and Effects of Heavy Metals in Fishes: Antioxidant Defense System, miRNA/Gene Expression Response, and Histopathological Reproductive Manifestations

Heavy metal pollution is a major environmental concern and in particular for aquatic ecosystems. With heavy metals exceeding safe and recommended limits, they pose significant threats to the environment and its inhabitants, including fish. Heavy metals, when accumulated in the different organs of the fish, result in toxicity in fish by producing reactive oxygen species (ROS) through the generation of oxidizing radicals. This oxidative stress mechanism is a key factor in the detrimental effects of heavy metal pollution on aquatic life. Heavy metal exposure profoundly affects fish behavior and physiology. In this review, an attempt was made to report the effects of heavy metals on fish physiology, focusing on toxicological effects on antioxidant enzymes, microRNAs (miRNAs) and molecular genetic responses, histopathology of organs, and underlying molecular mechanisms. This review also highlighted the heavy metal impact on fish gonads (testes and ovaries) and the hormones associated with it. The detection methods and the incorporation of latest developments in AI-based technology for the detection of heavy metals are also included in this review. Understanding the above effects is important for assessing the ecological impact of heavy metal pollution and developing strategies to mitigate its adverse effects on aquatic life. Understanding the consequences listed above is important for analyzing the ecological impact of heavy metal pollution and devising measures to reduce its negative effects on aquatic life and human health.